Internal combustion engine knocking judging device and knocking judging method

ABSTRACT

An engine ECU executes: calculating 15-degrees integrated value integrating vibration intensity for each of six crank angle ranges; detecting an amount of change in the 15-degrees integrated value between ignition cycles; specifying two ranges having larger amounts of change; specifying a crank angle having intensity larger than that of a neighboring crank angle in a search range determined to be the same as the specified ranges; calculating a coefficient of correlation K corresponding to a difference between a vibration waveform and a knock waveform model while the specified crank angle is matched with a timing at which intensity peaks in the knock waveform model; and, if the coefficient of correlation K is larger than a threshold value K( 0 ), determining that knock has occurred.

TECHNICAL FIELD

The present invention relates to a knock determination device and aknock determination method for an internal combustion engine and, morespecifically, to knock determination based on vibration waveform of theinternal combustion engine.

BACKGROUND ART

Conventionally, various methods of detecting knocking (knock) of aninternal combustion engine have been known. By way of example, atechnique has been known which determines that knock has occurred whenvibration intensity of an internal combustion engine is above athreshold value. It is possible, however, that noise such as vibrationexperienced when an intake valve or an exhaust valve is closed hasintensity higher than the threshold value, while knocking does notoccur. This may leads to an erroneous determination that knock hasoccurred, though knock has not occurred. Therefore, techniques fordetermining presence/absence of knocking based on vibration waveform totake into consideration characteristics other than the intensity, suchas crank angle at which vibration occurs or attenuation factor have beenproposed.

Japanese Patent Laying-Open No. 2003-021032 discloses a knock controldevice for an internal combustion engine, including a knock sensor fordetecting knocking of the internal combustion engine, a statisticalprocessing unit for statistically processing an output signal detectedby the knock sensor, a first temporary determining unit for determiningknock occurrence based on the result of processing by the statisticalprocessing unit, a second temporary determining unit for determiningknock occurrence based on the waveform of the output signal detected bythe knock sensor, and a final knock determining unit for finallydetermining knock occurrence based on the temporary knock determinationby the first temporary determining unit and the temporary knockdetermination by the second temporary determining unit. The secondtemporary determining unit temporarily determines occurrence of a knockbased on a determination period in which the output signal output fromthe knock sensor is above a prescribed value, and on a maximum value ofthe output signal detected in the determination period. The final knockdetermining unit finally determines that knock has occurred, if both thefirst and second temporary determining units determined that knock hasoccurred.

Assuming that the knock occurrence is determined temporarily based onthe determination period in which the output signal output from theknock sensor is above a prescribed value and on a maximum value of theoutput signal detected in the determination period as in the knockcontrol device described in Japanese Patent Laying-Open No. 2003-021032,erroneous determination may be made if vibration of high intensityoccurs regularly by a cause other than knocking in the internalcombustion engine. Further, as the knock occurrence is determined basedon the maximum value in the determination period in which the outputsignal output from the knock sensor is above a prescribed value,erroneous determination may be made if vibration caused not by knockinghas higher vibration intensity than the vibration caused by knocking.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a knock determinationdevice and a knock determination method for an internal combustionengine that can reduce erroneous determination.

According to an aspect, the present invention provides a knockdetermination device for an internal combustion engine, including aknock sensor detecting intensity of vibration of the internal combustionengine, and an operation unit. The operation unit detects a waveform ofvibration of the internal combustion engine based on the detectedintensity, calculates, for each of a predetermined plurality of crankangle ranges, an integrated value integrating the vibration intensity ofthe waveform, detects an amount of change in the integrated valuebetween ignition cycles, based on a difference between the integratedvalue and a predetermined value, specifies a predetermined number ofcrank angle ranges in which the amount of change in the integrated valueis larger, among the plurality of crank angle ranges, specifies a crankangle having an intensity higher than the intensity in a neighboringcrank angle, in a search range determined with reference to a specifiedcrank angle range, and while a timing at which intensity becomes thehighest in a waveform model defined as a reference of vibration in theinternal combustion engine is matched with the specified crank angle,based on a result of comparison between the waveform and the waveformmodel in this state, determines whether knock has occurred in theinternal combustion engine or not.

In this arrangement, vibration intensity of the internal combustionengine is detected. Based on the detected intensity, vibration waveformof the internal combustion engine is detected. An integrated valueintegrating vibration intensity of the waveform is calculated for eachof a plurality of predetermined crank angle ranges. Based on adifference between the integrated value and a predetermined value, anamount of change in the integrated value between ignition cycles isdetected. Among the plurality of crank angle ranges, a predeterminednumber of crank angle ranges in which the amount of change in theintegrated value is large are specified. In a search range determinedusing the specified crank angle range, a crank angle having higherintensity than a neighboring crank angle is specified. In this manner, acrank angle that can be considered to have vibration intensity changedbetween ignition cycles can be specified. In other words, a crank angleat which occurrence of knocking is highly possible, can be specified. Atiming at which intensity becomes the highest in a waveform modeldefined as a reference of vibration in the internal combustion engine ismatched with the specified crank angle and, based on a result ofcomparison between the waveform and the waveform model in this state,whether knock has occurred in the internal combustion engine or not isdetermined. Therefore, it becomes possible to determine whether knockhas occurred or not based on the portion where intensity abruptlyincreases in the detected waveform, and to avoid determination as towhether knock has occurred or not based on portions constantly havinghigh intensity. Therefore, false determination that knocking occurredwhen actually there is no knocking can be avoided. As a result,erroneous determination can be reduced.

Preferably, the operation unit determines that knock has not occurred inthe internal combustion engine if the specified crank angle is in apredetermined range.

In this arrangement, when the specified crank angle is in apredetermined range, it is determined that knock has not occurred in theinternal combustion engine. Therefore, even when vibration intensityincreases accidentally at a crank angle at which knocking occurrence isimpossible, false determination that knock has occurred when actuallythere is no knocking can be avoided.

More preferably, a range same as the specified crank angle range isdetermined to be the search range.

In this arrangement, from the crank angle range in which the amount ofchange in integrated value between ignition cycles is large, a vibrationpeak is detected. Therefore, it becomes possible to detect the vibrationpeak from the crank angle range at which knocking occurrence is highlypossible. Consequently, vibration peak derived from knocking can bespecified with high accuracy.

More preferably, a range including the specified crank angle range andwider than the specified crank angle range is determined to be thesearch range.

In this arrangement, the vibration peak is detected from a range thatencompasses the specified crank angle range and wider than the specifiedcrank angle range. Therefore, it becomes possible to detect thevibration peak from the vicinity of crank angle range in which theamount of change of the integrated value is large. Thus, it becomespossible to detect the vibration peak from the crank angle range atwhich knocking occurrence is highly possible. Consequently, vibrationpeak derived from knocking can be specified with high accuracy.

More preferably, the operation unit determines that knock has notoccurred in the internal combustion engine if a crank angle havinghigher intensity than a neighboring crank angle does not exist in thesearch range.

In this arrangement, if there is no crank angle having higher intensitythan a neighboring crank angle in the search range, it is determinedthat knock has not occurred in the internal combustion engine.Therefore, it becomes possible to determine that knock has not occurredin the internal combustion engine, if a vibration peak cannot be found.Therefore, even when vibration intensity increases accidentally at acrank angle at which knocking occurrence is impossible, for example,outside the search range, false determination that knock has occurredwhen actually there is no knocking can be avoided.

More preferably, the operation unit detects the amount of change in theintegrated value between ignition cycles, based on an absolute value ofdifference between the integrated value and the predetermined value.

In this arrangement, the amount of change in the integrated valuebetween ignition cycles is detected, from the absolute value ofdifference between the integrated value and the predetermined value.Therefore, even if the integrated value decreases as in the case whenknocking of low intensity follows knocking of high intensity, the amountof change in the integrated value can be calculated.

More preferably, the operation unit calculates ratio of the amount ofchange of the integrated value with respect to a sum of amounts ofchange in the integrated value. A number corresponding to the calculatedratio is determined to be the predetermined number.

In this arrangement, the crank angle ranges in which the amount ofchange in integrated value is large are specified by the number thatcorresponds to the ratio of amount of change of each integrated valuewith respect to the total sum of the amounts of change of integratedvalues. By way of example, if only one ratio among the ratios is largerthan the predetermined ratio, “1” is defined as the predeterminednumber. Therefore, if it is the case that the amount of change of theintegrated value is large only in one range, it is possible to avoidspecifying unnecessarily larger number of ranges. Consequently, itbecomes possible to avoid specifying a range of which relative amount ofchange of the integrated value is large but absolute amount of change ofthe integrated value is small. As a result, it becomes possible to avoiderroneous specification of a crank angle at which vibration peaks, fromthe crank angle range in which knocking occurrence is unlikely.

More preferably, if at least one of the ratios is larger than apredetermined ratio, 1 is determined to be the predetermined number.

In this arrangement, if at least one of the ratios is higher than thepredetermined ratio, “1” is defined as the predetermined number.Consequently, it becomes possible to avoid specifying a range of whichrelative amount of change of the integrated value is large but absoluteamount of change of the integrated value is small. As a result, itbecomes possible to avoid erroneous detection of a vibration peak fromthe crank angle range in which knocking occurrence is unlikely.

More preferably, vibration intensity and the waveform of the internalcombustion engine are detected in a plurality of ignition cycles. Theintegrated value is calculated for each ignition cycle. Thepredetermined value is an integrated value of an ignition cyclepreceding the ignition cycle in which the waveform to be compared withthe waveform model is detected.

In this arrangement, the integrated value is calculated for eachignition cycle. The predetermined value is the integrated value in theignition cycle prior to the ignition cycle in which the waveform to becompared with the waveform model is detected. Therefore, the amount ofchange in the integrated value between ignition cycles can be detected.

More preferably, the predetermined value is an integrated value of anignition cycle preceding the ignition cycle in which the waveform to becompared with the waveform model is detected and satisfying a conditionthat maximum vibration intensity is smaller than a predeterminedintensity.

In this arrangement, the predetermined value is the integrated value inthe ignition cycle prior to the ignition cycle in which the waveform tobe compared with the waveform model is detected and satisfying thecondition that the maximum value of vibration intensity is smaller thanthe predetermined intensity. Therefore, it becomes possible to detectthe amount of change of the integrated value using the integrated valueof the ignition cycle of which maximum vibration intensity is smallerthan a predetermined intensity, that is, the ignition cycle consideredto be free of knocking, as a reference. Consequently, it becomespossible to prevent decrease in the amount of change in the integratedvalue despite the fact that actually knock has occurred. As a result, itbecomes possible to specify with high accuracy a range in which knockingcould possibly have occurred.

More preferably, the predetermined value is an integrated value of anignition cycle preceding the ignition cycle in which the waveform to becompared with the waveform model is detected and continuouslysatisfying, for more than a predetermined number of times, the conditionthat maximum vibration intensity is larger than a predeterminedintensity.

In this arrangement, the predetermined value is the integrated value inthe ignition cycle prior to the ignition cycle in which the waveform tobe compared with the waveform model is detected and continuouslysatisfying for more than a prescribed number of times the condition thatthe maximum value of vibration intensity is larger than thepredetermined intensity. Therefore, even if the vibration intensity ishigh, it can be used as a reference for calculating the amount of changeof the integrated value as long as it is in a steady state.Consequently, erroneous determination of a vibration having highintensity caused not by knocking to be the vibration caused by knockingcan be avoided.

More preferably, the predetermined value is an operation value obtainedby smoothing the integrated value.

In this arrangement, the operation value obtained by smoothing theintegrated value is used as the predetermined value. Therefore, itbecomes possible to detect the amount of change in the integrated valueusing the operation value that does not change much between ignitioncycles. Consequently, it becomes possible to prevent such a situationthat references for detecting the amount of change of the integratedvalue differ considerably from one ignition cycle to another. As aresult, stable and highly accurate determination of knocking occurrencebecomes possible.

More preferably, the predetermined value is an operation value obtainedby smoothing the integrated value in an ignition cycle of which maximumvibration intensity is smaller than a predetermined intensity.

In this arrangement, an operation value obtained by smoothing theintegrated value of the ignition cycle of which maximum vibrationintensity is smaller than the predetermined intensity is used as thepredetermined value. Consequently, it is possible to calculate theoperation value from, for example, integrated value excluding theintegrated value of that ignition cycle in which knocking occurred.Therefore, the amount of change of the integrated value is detectedbased on the operation value that does not change much between ignitioncycles. Consequently, it becomes possible to prevent such a situationthat references for detecting the amount of change of the integratedvalue differ considerably from one ignition cycle to another. As aresult, stable and highly accurate determination of knocking occurrencebecomes possible.

More preferably, the operation unit calculates a value corresponding toa difference between the waveform and the waveform model such that thevalue becomes larger as the difference between the waveform and thewaveform model becomes smaller, and when the value corresponding to thedifference becomes larger than a threshold value, determines that knockhas occurred.

In this arrangement, the value corresponding to the difference betweenthe waveform and the waveform model is calculated, which value is madelarger as the difference between the waveform and the waveform model issmaller. When the value corresponding to the difference is larger thanthe threshold value, knocking is determined to have occurred. Thus, itis possible to determine whether knock has occurred or not with highaccuracy based on the waveform.

According to another aspect, the present invention provides a knockdetermination device for an internal combustion engine, including aknock sensor detecting intensity of vibration of the internal combustionengine, and an operation unit. The operation unit detects a waveform ofvibration of the internal combustion engine based on the detectedintensity, calculates, for each of a predetermined plurality of crankangle ranges, an integrated value integrating the vibration intensity ofthe waveform, detects an amount of change in the integrated valuebetween ignition cycles for each of the plurality of crank angle ranges,specifies a predetermined number of crank angle ranges in which theamount of change in the integrated value is larger, among the pluralityof crank angle ranges, determines whether the integrated value in thespecified range has changed not because of knocking, if it is determinedthat the integrated value in the specified range has changed not becauseof knocking, corrects the detected vibration waveform such that amountof change in the integrated value in the specified range becomessmaller, calculates for each of the plurality of crank angle ranges, anintegrated value integrating vibration intensities of the correctedwaveform, and determines whether knock has occurred or not using a sumof each of the integrated values of the corrected waveform.

In this arrangement, vibration intensity of the internal combustionengine is detected. Based on the detected intensity, vibration waveformof the internal combustion engine is detected. An integrated valueintegrating vibration intensity of the waveform is calculated for eachof a plurality of predetermined crank angle ranges. An amount of changeof the integrated value between ignition cycles is detected. Among theplurality of crank angle ranges, a predetermined number of crank angleranges in which the amount of change in the integrated value is largerare specified. In this manner, a crank angle range that can beconsidered to have vibration intensity changed between ignition cyclescan be specified. In other words, a crank angle range at whichoccurrence of knocking is highly possible, can be specified. It isnoted, however, that vibration intensity can abruptly increase notbecause of knocking. Therefore, if it is determined that the integratedvalue in the specified range has changed not because of knocking, thedetected vibration waveform is corrected such that the amount of changeof the integrated value in the specified range becomes small.Consequently, it becomes possible to exclude from the detected waveformthat portion which has intensity increased abruptly by a factordifferent from knocking (for example, operation of a component of theinternal combustion engine). The integrated value obtained byintegrating vibration intensity of the corrected waveform is calculatedfor each of the plurality of crank angle ranges. Using the sum ofintegrated values of corrected waveforms, whether knock has occurred ornot is determined. Therefore, it is possible to determine whether knockhas occurred or not using the waveform not much influenced by theintensity increased not by knocking. Therefore, erroneous determinationof knocking occurrence can be avoided. As a result, a knockdetermination device or a knock determination method for an internalcombustion engine that can reduce erroneous determination can beprovided.

Preferably, if it is determined that the integrated value in thespecified ranges has changed not because of knocking, the operation unitcorrects the detected vibration waveform such that the integrated valueof the specified range becomes equal to an integrated value calculatedin the last ignition cycle, so that the amount of change of theintegrated value becomes smaller.

In this arrangement, the detected vibration waveform is corrected suchthat the integrated value in the specified range becomes equal to theintegrated value calculated in the previous ignition cycle.Consequently, it becomes possible to exclude from the detected waveformthat portion which has intensity increased abruptly by a factordifferent from knocking.

More preferably, the operation unit detects the amount of change of theintegrated value based on a difference of the integrated values ofcontinuous ignition cycles.

In this arrangement, it is possible to detect the amount of change ofthe integrated value from the difference of the integrated values ofcontinuous ignition cycles.

More preferably, the operation unit detects the amount of change of theintegrated value based on an absolute value of difference of theintegrated values of continuous ignition cycles.

In this arrangement, it is possible to detect the amount of change ofthe integrated value from the absolute value of difference of theintegrated values of continuous ignition cycles.

More preferably, the operation unit calculates an operation value bysmoothing the integrated value for each of the plurality of crank angleranges, and if it is determined that the integrated value in thespecified range has changed not because of knocking, corrects thedetected vibration waveform such that the integrated value of thespecified range becomes equal to the operation value, so that the amountof change of the integrated value becomes smaller.

In this arrangement, the detected vibration waveform is corrected suchthat the integrated value of the specified range becomes equal to theoperation value obtained by smoothing the integrated value. Thus, itbecomes possible to exclude from the detected waveform that portionwhich has intensity increased abruptly by a factor different fromknocking.

More preferably, the operation unit detects the amount of change of theintegrated value based on a difference between the integrated value andthe operation value.

In this arrangement, it is possible to detect the amount of change ofthe integrated value from the difference between the integrated valueand the operation value.

More preferably, the operation unit detects the amount of change of theintegrated value based on an absolute value of difference between theintegrated value and the operation value.

In this arrangement, it is possible to detect the amount of change ofthe integrated value from the absolute value of difference between theintegrated value and the operation value.

More preferably, the operation unit specifies a crank angle having anintensity higher than the intensity of a neighboring crank angle, in asearch range determined with reference to the specified range, and whilea timing at which intensity becomes the highest in a waveform modeldefined as a reference of vibration in the internal combustion engine ismatched with the specified crank angle, based on a result of comparisonbetween the waveform and the waveform model in this state, determineswhether the integrated value in the specified range has changed notbecause of knocking.

In a search range determined using the specified range, a crank anglehaving higher intensity than a neighboring crank angle is specified. Inthis manner, a crank angle that can be considered to have vibrationintensity changed between ignition cycles can be specified. In otherwords, a crank angle at which occurrence of knocking is highly possible,can be specified. A timing at which intensity becomes the highest in awaveform model defined as a reference of vibration in the internalcombustion engine is matched with the specified crank angle and, basedon a result of comparison between the waveform and the waveform model inthis state, whether knock has occurred in the internal combustion engineor not is determined. Therefore, it becomes possible to determinewhether knock has occurred or not based on the portion where intensityabruptly increases in the detected waveform, and to avoid determinationas to whether knock has occurred or not based on portions constantlyhaving high intensity. Therefore, false determination that knock hasoccurred when actually there is no knocking can be avoided. As a result,a knock determination device or a knock determination method for aninternal combustion engine that can reduce erroneous determination canbe provided.

More preferably, the operation unit calculates a coefficientcorresponding to a difference between the waveform and the waveformmodel such that the coefficient becomes larger as the difference betweenthe waveform and the waveform model becomes smaller, and determines, ifthe coefficient is larger than a threshold value, that the integratedvalue in the specified range has changed because of knocking, anddetermines, if the coefficient is smaller than the threshold, that theintegrated value in the specified range has changed not because ofknocking.

In this arrangement, the coefficient corresponding to the differencebetween the waveform and the waveform model is calculated, whichcoefficient is made larger as the difference between the waveform andthe waveform model is smaller. The larger the coefficient, the higherbecomes the possibility that knocking occurred. Therefore, when thecoefficient is larger than the threshold value, it is determined thatthe integrated value in the specified range has changed because ofknocking. On the contrary, if the coefficient is smaller than thethreshold value, it is determined that the integrated value in thespecified range has changed not because of knocking. Thus, it ispossible to determine with high accuracy whether the integrated valuehas changed because of knocking or not.

More preferably, the operation unit determines, if the specified crankangle is in a predetermined range, that the integrated value in thespecified range has changed not because of knocking.

In this arrangement, if the specified crank angle is in thepredetermined range, it is determined that the integrated value in thespecified range has changed not because of knocking. Therefore, evenwhen vibration intensity increases accidentally at a crank angle atwhich knocking occurrence is impossible, false determination that knockhas occurred when actually there is no knocking can be avoided.

More preferably, the operation unit specifies a plurality of crank angleranges in which the amount of change in the integrated value is larger,among the plurality of crank angle ranges, and the operation unitdetermines whether the integrated values in the plurality of specifiedranges have changed not because of knocking.

In this arrangement, a plurality of crank angle ranges in which theamount of change of the integrated value is larger are specified.Whether the integrated value in the plurality of specified ranges havechanged because of knocking or not is determined. Consequently, theaccuracy in specifying the range in which the integrated value haschanged not because of knocking can be enhanced.

More preferably, if it is determined that the integrated value in atleast one of the plurality of specified ranges has changed because ofknocking, the operation unit inhibits correction of the detectedwaveform.

In this arrangement, if it is determined that the integrated value in atleast one of the plurality of specified ranges has changed because ofknocking, whether knock has occurred or not is determined using the sumof integrated values calculated with the detected waveforms notcorrected. This simplifies the process.

Further preferably, if it is determined that the integrated value in atleast one of the plurality of specified ranges has changed not becauseof knocking, the operation unit corrects the detected vibration waveformsuch that the amount of change in the integrated value in the range inwhich the integrated value is determined to have changed not because ofknocking becomes smaller.

In this arrangement, if it is determined that the integrated value in atleast one of the plurality of specified ranges has changed not becauseof knocking, the detected vibration waveform is corrected such that theamount of change of the integrated value in the range of whichintegrated value is determined to have changed not because of knockingbecomes small. Consequently, it becomes possible to exclude from thedetected waveform that portion which has intensity increased abruptly bya factor different from knocking.

More preferably, the operation unit corrects a determination value usedfor determining whether knock has occurred or not, using a sum of theintegrated values of the corrected waveform, and determines whetherknock has occurred or not based on a result of comparison betweenvibration intensity of the internal combustion engine and the correcteddetermination value, and thereby determines whether knock has occurredor not using the sum of each of the integrated values of the correctedwaveform. In this arrangement, the determination value used fordetermining whether knock has occurred or not is corrected using the sumof respective integrated values of corrected waveforms. Whether knockhas occurred or not is determined based on the result of comparison ofthe vibration intensity of the internal combustion engine and correcteddetermination value, and hence, whether knock has occurred or not isdetermined using the sum of integrated values of the corrected waveform.Accordingly, it becomes possible to determine with high accuracy whetherknock has occurred or not, using the determination value that iscorrected in consideration of vibration characteristic of eachindividual internal combustion engine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic configuration diagram showing an engine controlledby an engine ECU as a knock determination device in accordance with afirst embodiment of the present invention.

FIG. 2 shows frequency bands of vibrations generated in the engine whenknock occurs.

FIG. 3 is a control block diagram showing the engine ECU of FIG. 1.

FIG. 4 shows an engine vibration waveform.

FIG. 5 shows a knock waveform model stored in an ROM of the engine ECU.

FIG. 6 shows comparison between the vibration waveform and the knockwaveform model.

FIG. 7 shows a map of determination value V(J) stored in an ROM or anSRAM of engine ECU.

FIG. 8 is a (first) diagram representing frequency distribution ofintensity value LOG(V).

FIG. 9 is a (first) diagram representing amount of change of 15-degreesintegrated value.

FIG. 10 is a functional block diagram of engine ECU as the knockdetermination device in accordance with the first embodiment of thepresent invention.

FIG. 11 is a flowchart representing a control structure of a programexecuted by engine ECU as the knock determination device in accordancewith the first embodiment of the present invention.

FIG. 12 is a functional block diagram of engine ECU as the knockdetermination device in accordance with a second embodiment of thepresent invention.

FIG. 13 is a flowchart representing a control structure of a programexecuted by engine ECU as the knock determination device in accordancewith the second embodiment of the present invention.

FIG. 14 is a (second) diagram representing amount of change of15-degrees integrated value.

FIG. 15 shows a crank angle search range in which the intensity peaks,in a third embodiment of the present invention.

FIG. 16 is a functional block diagram of engine ECU as the knockdetermination device in accordance with a fourth embodiment of thepresent invention.

FIG. 17 is a flowchart representing a control structure of a programexecuted by engine ECU as the knock determination device in accordancewith the fourth embodiment of the present invention.

FIG. 18 is a (third) diagram representing amount of change of 15-degreesintegrated value.

FIG. 19 is a functional block diagram of engine ECU as the knockdetermination device in accordance with a fifth embodiment of thepresent invention.

FIG. 20 is a flowchart representing a control structure of a programexecuted by engine ECU as the knock determination device in accordancewith the fifth embodiment of the present invention.

FIG. 21 is a (fourth) diagram representing amount of change of15-degrees integrated value.

FIG. 22 is a (second) diagram representing frequency distribution ofintensity value LOG(V).

FIG. 23 is a flowchart representing a control structure of a programexecuted by engine ECU as the knock determination device in accordancewith a sixth embodiment of the present invention.

FIG. 24 is a flowchart representing a control structure of a programexecuted by engine ECU as the knock determination device in accordancewith a seventh embodiment of the present invention.

FIG. 25 is a functional block diagram of engine ECU as the knockdetermination device in accordance with an eighth embodiment of thepresent invention.

FIG. 26 is a flowchart representing a control structure of a programexecuted by engine ECU as the knock determination device in accordancewith the eighth embodiment of the present invention.

FIG. 27 is a flowchart representing a control structure of a programexecuted by engine ECU as the knock determination device in accordancewith a ninth embodiment of the present invention.

FIG. 28 is a (third) diagram representing frequency distribution ofintensity value LOG(V).

FIG. 29 is a functional block diagram of engine ECU as the knockdetermination device in accordance with a tenth embodiment of thepresent invention.

FIG. 30 is a (first) flowchart representing a control structure of aprogram executed by engine ECU as the knock determination device inaccordance with the tenth embodiment of the present invention.

FIG. 31 is a (second) flowchart representing a control structure of aprogram executed by engine ECU as the knock determination device inaccordance with the tenth embodiment of the present invention.

FIG. 32 is a (fifth) diagram representing amount of change of 15-degreesintegrated value.

FIG. 33 shows corrected vibration waveform.

BEST MODES FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described in the followingwith reference to the figures. In the following description, the samecomponents are denoted by the same reference characters. The names andfunctions are also the same. Therefore, detailed description thereofwill not be repeated.

First Embodiment

Referring to FIG. 1, an engine 100 of a vehicle mounting the knockdetermination device in accordance with an embodiment of the presentinvention will be described. Engine 100 is provided with a plurality ofcylinders. The knock determination device in accordance with the presentembodiment is realized by executing a program stored, for example, in anROM (Read Only Memory) 202 of an engine ECU (Electronic Control Unit)200.

Engine 100 is an internal combustion engine, in which a mixture of airtaken through an air cleaner 102 and a fuel injected by an injector 104is ignited by a spark plug 106 and burned in a combustion chamber.Though timing of ignition is adjusted to attain MBT (Minimum advance forBest Torque) to maximize output torque, it is advanced or retarded inaccordance with the state of operation of engine 100 when, for example,knocking occurs.

The burning of air-fuel mixture causes combustion pressure that pressesa piston 108 down, whereby a crankshaft 110 rotates. The combustedair-fuel mixture (or exhaust gas) is purified by a three-way catalyst112 and thereafter discharged outside the vehicle. The amount of airtaken into engine 100 is adjusted by a throttle valve 114.

Engine 100 is controlled by engine ECU 200 having connected thereto aknock sensor 300, a water temperature sensor 302, a crank positionsensor 306 arranged opposite to a timing rotor 304, a throttle openposition sensor 308, a vehicle speed sensor 310, an ignition switch 312and an air flow meter 314.

A knock sensor 300 is provided in a cylinder block of engine 100. Knocksensor 300 is implemented by a piezoelectric element. As engine 100vibrates, knock sensor 300 generates a voltage having a magnitudecorresponding to that of the vibration. Knock sensor 300 transmits asignal representing the voltage to engine ECU 200. Water temperaturesensor 302 detects temperature of cooling water in engine 100 at a waterjacket and transmits a signal representing a resultant detection toengine ECU 200.

Timing rotor 304 is provided at crankshaft 110 and rotates together withcrankshaft 110. Timing rotor 304 is circumferentially provided with aplurality of protrusions spaced by a predetermined distance. Crankposition sensor 306 is arranged opposite to the protrusions of timingrotor 304. When timing rotor 304 rotates, an air gap between theprotrusions of timing rotor 304 and crank position sensor 306 varies, sothat magnetic flux passing through a coil portion of crank positionsensor 306 increases/decreases, thus generating electromotive force.Crank position sensor 306 transmits a signal representing theelectromotive force to engine ECU 200. From the signal transmitted fromcrank position sensor 306, engine ECU 200 detects a crank angle androtation number of crankshaft 110.

Throttle open position sensor 308 detects a throttle open position andtransmits a signal representing a resultant detection to engine ECU 200.Vehicle speed sensor 310 detects number of rotations of a wheel (notshown) and transmits a signal representing a resultant detection toengine ECU 200. From the number of rotations of the wheel, engine ECU200 calculates the vehicle speed. Ignition switch 312 is turned on by adriver, for starting engine 100. Air flow meter 314 detects amount ofair taken into engine 100, and transmits a signal representing aresultant detection to engine ECU 200.

Engine ECU 200 operates with electric power fed from an auxiliarybattery 320. Engine ECU 200 uses the signals transmitted from varioussensors and ignition switch 312 as well as maps and programs stored inROM 202 and an SRAM (Static Random Access Memory) 204 to perform anoperation to control equipment so that engine 100 attains a desireddriving condition.

In the present embodiment, using a signal transmitted from knock sensor300 and a crank angle, engine ECU 200 detects a waveform of vibration(hereinafter referred to as “vibration waveform”) of engine 100 at apredetermined knock detection gate (a section from a predetermined firstcrank angle to a predetermined second crank angle) and from the detectedvibration waveform determines whether knock has occurred in engine 100.The knock detection gate of the present embodiment is from the top deadcenter (0°) to 90° in a combustion stroke. It is noted that the knockdetection gate is not limited thereto. The knock detection gatecorresponds to the first range of the first invention described above.

When the engine knocks, vibrations occur in engine 100 at frequenciesaround the frequencies represented by solid lines in FIG. 2. Thefrequency of vibration caused by knocking is not constant but has aprescribed bandwidth. Therefore, in the present embodiment, vibrationsat frequencies included in a first frequency band A, a second frequencyband B, and a third frequency band C are detected, as shown in FIG. 2.In FIG. 2, CA represents crank angle. The number of frequency bandsincluding the frequencies of vibration attributed to knocking is notlimited to three.

Referring to FIG. 3, engine ECU 200 will further be described. EngineECU 200 includes an A/D (analog/digital) converting unit 400, aband-pass filter (1) 410, a band-pass filter (2) 420, a band-pass filter(3) 430, and an integrating unit 450.

A/D converting unit 400 converts an analog signal transmitted from knocksensor 300 to a digital signal. Band-pass filter (1) 410 passes only thesignal in the first frequency band A of the signals transmitted fromknock sensor 300. Specifically, of the vibrations detected by knocksensor 300, only the vibrations in the first frequency band A areextracted by band-pass filter (1) 410.

Band-pass filter (2) 420 passes only the signal in the second frequencyband B of the signals transmitted from knock sensor 300. Specifically,of the vibrations detected by knock sensor 300, only the vibrations inthe second frequency band B are extracted by band-pass filter (2) 420.

Band-pass filter (3) 430 passes only the signal in the third frequencyband C of the signals transmitted from knock sensor 300. Specifically,of the vibrations detected by knock sensor 300, only the vibrations inthe third frequency band C are extracted by band-pass filter (3) 430.

Integrating unit 450 integrates the signals selected by band-pass filter(1) 410 to band-pass filter (3) 430, that is, vibration intensities,five degrees by five degrees of the crank angle. In the following, thevalue integrated for five degrees of crank angle will be denoted as5-degrees integrated value. Calculation of 5-degrees integrated value isdone for each frequency band. Calculation of 5-degrees integrated valuerealizes detection of frequency waveform in each frequency band.

Further, the thus calculated 5-degrees integrated values of the firstfrequency band A to the third frequency band C are added incorrespondence with the crank angle. Specifically, vibration waveformsof the first frequency band A to the third frequency band C arecombined.

Consequently, the vibration waveform of engine 100 is detected as shownin FIG. 4. The combined waveform of the first to third frequency bands Ato C is used as the vibration waveform of engine 100.

The detected vibration waveform is compared with the knock waveformmodel stored in ROM 202 of engine ECU 200 as shown in FIG. 5. The knockwaveform model is formed in advance as a model vibration waveform whenengine 100 knocks.

In the knock waveform model, magnitude of vibration is represented by adimensionless number of 0 to 1 and does not uniquely correspond to acrank angle. More specifically, for the knock waveform model of thepresent embodiment, while it is determined that the vibration intensitydecreases as the crank angle increases after the peak value of vibrationintensity, the crank angle at which the vibration intensity assumes thepeak value is not determined.

The knock waveform model of the present embodiment corresponds to thevibration after the peak intensity of vibration generated by knocking. Aknock waveform model that corresponds to vibration after the rise ofvibration caused by knocking may be stored.

The knock waveform model is formed and stored in advance based on avibration waveform of engine 100 detected when knocking is forced by anexperiment or the like.

The knock waveform model is formed by using an engine 100 (hereinafterreferred to as central characteristic engine) of which size and outputvalue of knock sensor 300 are the central values of size tolerance andoutput tolerance of knock sensor 300. In other words, the knock waveformmodel is the vibration waveform obtained when knocking is forced in thecentral characteristic engine. The method of forming the knock waveformmodel is not limited thereto, and it may be formed, by way of example,by simulation.

In the comparison between the detected waveform and the knock waveformmodel, a normalized waveform and the knock waveform model are compared,as shown in FIG. 6. Here, normalization refers, for instance, torepresentation of vibration intensity by a dimensionless number of 0 to1, by dividing each five-degrees integrated value by a five-degreesintegrated value larger than a five-degrees integrated value ofneighboring crank angle and the largest among such five-degreesintegrated values, that is, the peak of five-degrees integrated value.The method of normalization is not limited thereto.

In the present embodiment, engine ECU 200 calculates a coefficient ofcorrelation K, which is a value related to a deviation between thenormalized vibration waveform and the knock waveform model. The crankangle at which intensity (5-degrees integrated value) of the vibrationwaveform peaks is matched with a timing at which the intensity of knockwaveform model peaks, and in this state, absolute value of deviation(amount of displacement) between the normalized vibration waveform andthe waveform model is calculated crank angle by crank angle (at every 5degrees), whereby the coefficient of correlation K is calculated. Here,the method of specifying the crank angle at which the intensity peaks inthe vibration waveform will be described in detail later.

When we represent the absolute value of deviation between the normalizedvibration waveform and the knock waveform model for each crank angle byΔS(I) (wherein I is a natural number) and the vibration intensity ofknock waveform model integrated by the crank angle (i.e., the area ofknock waveform model) by S, then the coefficient of correlation K iscalculated by an equation K=(S−ΣΔS(I))/S, where ΣΔS(I) represents a sumof ΔS(I)s. In the present embodiment, coefficient of correlation K iscalculated as a larger value when the signal waveform has a shape closerto the knock waveform model. Therefore, if the vibration waveformincludes vibration waveform caused not by knocking, the calculatedcoefficient of correlation K comes to have a smaller value. Note thatthe coefficient of correlation K may be calculated by a differentmethod.

Further, engine ECU 200 calculates a knock intensity N based on themaximum value among the 5-degrees integrated values. When we representthe maximum value of 5-degrees integrated values by P and the valuerepresenting the magnitude of vibration of engine 100 while engine 100is not knocking by BGL (Back Ground Level), the nock intensity N iscalculated by the equation N=P/BGL. The maximum value P of 5-degreesintegrated value for calculating knock intensity N is subjected tologarithmic conversion. Note that the knock intensity N may becalculated by a different method.

The value BGL is calculated by subtracting, in the frequencydistribution of intensity value LOG(V), which will be described later, aproduct of standard deviation σ and a coefficient (for example, “1”)from the median V(50). BGL may be calculated by a different method, andBGL may be stored in ROM 202.

In the present embodiment, engine ECU 200 compares the calculated knockintensity N with the determination value V(J) stored in SRAM 204, andfurther compares the detected waveform with the stored knock waveformmodel, and determines for every one ignition cycle (720 degrees of crankangle) whether knock has occurred in engine 100 or not.

As shown in FIG. 7, the determination value V(J) is stored as a map, foreach of the ranges divided by the state of operation using engine speedNE and intake air amount KL as parameters. In the present embodiment,nine ranges are provided for each cylinder, by the division inaccordance with low speed (NE<NE(1)), middle speed (NE(1)≦NE<NE(2)),high speed (NE(2)≦NE), low burden (KL≦KL(1)), middle burden(KL(1)≦KL<KL(2)) and high burden (KL(2)≦KL). The number of ranges is notlimited thereto. Further, ranges may be divided using a parameter orparameters other than the engine speed NE and intake air amount KL.

At the time of shipment of engine 100 or the vehicle, a value determinedin advance through an experiment or the like is used as thedetermination value V(J) (initial determination value V(J) at shipment)stored in ROM 202. Dependent on variation in output values ordegradation of knock sensor 300, detected intensity may possibly varyeven if the vibration occurring in engine 100 is the same. In that case,it is necessary to correct the determination value V(J) and to determinewhether knock has occurred or not using the determination value V(J)appropriate for the actually detected intensity.

Therefore, in the present embodiment, a knock determination level V(KD)is calculated based on a frequency distribution representing relationbetween an intensity value LOG(V) obtained by logarithmic conversion ofintensity V and frequency (number of times, or probability) of detectionof each intensity value LOG(V).

For every range defined by the engine speed NE and the intake air amountKL as parameters, the intensity value LOG(V) is calculated. Theintensity V used for calculating intensity value LOG(V) is the maximumintensity (maximum 5-degrees integrated value) of the detected waveform.Based on the calculated intensity value LOG(V), the median V(50) atwhich the frequency of intensity value LOG(V) accumulated from theminimum value attains 50% is calculated. Further, standard deviation σof intensity value LOG(V) not larger than the median V(50) iscalculated. By way of example, in the present embodiment, the medianV(50) and standard deviation σ, which are approximated to the median andstandard deviation calculated based on a plurality (for example, 200cycles) of intensity values LOG(V), are calculated by the followingmethod, cycle by cycle of ignition.

If the intensity value LOG(V) detected at present is larger than themedian V(50) calculated last time, a value obtained by adding apredetermined value C(1) to the median (50) calculated last time isprovided as the median V(50) this time. On the contrary, if theintensity value LOG(V) detected at present is smaller than the medianV(50) calculated last time, a value obtained by subtracting apredetermined value C(2) (by way of example, the value C(2) may be thesame as C(1)) from the median (50) calculated last time is provided asthe median V(50) this time.

If the intensity value LOG(V) detected this time is smaller than themedian V(50) calculated last time and larger than a value obtained bysubtracting the standard deviation σ calculated last time from themedian V(50) calculated last time, a value obtained by subtractingdouble a predetermined value C(3) from the standard deviation σcalculated last time is provided as the standard deviation σ this time.On the contrary, if the intensity value LOG(V) detected at present islarger than the median V(50) calculated last time, or if it is smallerthan the value obtained by subtracting the standard deviation σcalculated last time from the median V(50) calculated last time, a valueobtained by adding a predetermined value C(4) (by way of example, thevalue C(4) may be the same as C(3)) to the standard deviation σcalculated last time is provided as the standard deviation σ this time.The median V(50) and the standard deviation σ may be calculated by othermethods. Further, initial values of the median V(50) and the standarddeviation σ may be preset values, or “0”.

Using the median V(50) and the standard deviation σ, the knockdetermination level V(KD) is calculated. As shown in FIG. 8, a valueobtained by adding a product of a coefficient U(1) (U(1) is a constantand, for example, U(1)=3) and standard deviation σ to the median V(50)is provided as the knock determination level V(KD). The knockdetermination level V(KD) may be calculated by a different method.

The ratio (frequency) of intensity values LOG(V) larger than the knockdetermination level V(KD) is determined to be the frequency of knocking,and counted as knock occupation ratio KC.

If the knock occupation ratio KC is larger than a threshold value KC(O),the determination value V(J) is corrected to be smaller by apredetermined correction amount A(1), so that frequency of retardingignition timing increases. The corrected determination value V(J) isstored in SRAM 204.

The coefficient U(1) is a coefficient found from data and knowledgeobtained through experiment or the like. The intensity value LOG(V)larger than the knock determination level when U(1)=3 is substantiallyequal to the intensity value LOG(V) of the ignition cycle in which knockactually occurred. A value other than “3” may be used as coefficientU(1).

In the following, a method of specifying a crank angle at whichintensity peaks in the vibration waveform will be described.

In the present embodiment, a 15-degrees integrated value integrating theintensity for each range defined by equally dividing the knock detectiongate by 6, that is, for every crank angle of 15 degrees (three 5-degreesintegration values) is calculated, as shown in FIG. 9. The 15-degreesintegrated value is calculated for every few ignition cycles. The15-degrees integrated value corresponds to the integrated value in thefirst invention described above. The number of ranges is not limited to6, and any number of ranges may be used, as long as it is not smallerthan 2.

From the difference between the 15-degrees integrated value of thepresent ignition cycle and the 15-degrees integrated value of the last(one preceding) ignition cycle, the amounts of change ΔV(1)˜ΔV(6)represented by hatched lines in FIG. 9 are detected.

From the six ranges of which amounts of change ΔV(1)˜ΔV(6) of 15-degreesintegrated value are detected, two ranges having largest amounts ofchange are specified. The number of ranges to be specified is notlimited to two.

Ranges that are the same as the specified ranges are determined to be asearch range, and in the search range, a crank angle having intensity(five-degrees integrated value) higher than that of a neighboring crankangle and the highest among such intensities (five-degrees integratedvalue) is specified. Specifically, a crank angle at which the intensitypeaks in the vibration waveform is specified. The crank angle is matchedwith the timing when vibration intensity is maximized in the knockwaveform model, and the vibration waveform is compared with the knockwaveform model.

Referring to FIG. 10, functions of engine ECU 200 as a knockdetermination device in accordance with the present embodiment will bedescribed. The functions of engine ECU 200 described in the followingmay be implemented by hardware or software.

Engine ECU 200 includes an intensity detecting unit 210, a waveformdetecting unit 212, a knock intensity calculating unit 220, acorrelation coefficient calculating unit 222, a knock determination unit230, a 15-degrees integrated value calculating unit 240, a change amountdetecting unit 242, a range specifying unit 250, and a crank anglespecifying unit 252.

Intensity detecting unit 210 detects intensity V of vibration in theknock detection gate, based on the signal transmitted from knock sensor300. Waveform detecting unit 212 detects vibration waveform in the knockdetection gate by integrating vibration intensities V, 5 degrees by 5degrees of crank angle.

Knock intensity calculating unit 220 calculates the knock intensity N.Correlation coefficient calculating unit 222 calculates the coefficientof correlation K. Knock determination unit 230 determines that knock hasoccurred, if the knock intensity N is larger than the determinationvalue V(J) and the coefficient of correlation K is larger than thethreshold value K(0).

The 15-degrees integrated value calculating unit 240 calculates15-degrees integrated value for each of the ranges obtained by equallydividing the knock detection gate by 6. Change amount detecting unit 242detects amounts of change ΔV(1) to Δ(6) of 15-degrees integrated value.

Range specifying unit 250 specifies a range of the crank angle in whichthe detected amount of change of 15-degrees integrated value is larger,from the six ranges. In the present embodiment, range specifying unit250 specifies two ranges of which detected amount of change of15-degrees integrated value is larger.

Crank angle specifying unit 252 specifies, in the search rangedetermined to be the same range as the specified range, the crank angleof which intensity is larger than that of a neighboring crank angle andthe largest among such intensities.

Referring to FIG. 11, control structure of a program executed by engineECU 200 as the knock determination device in accordance with the presentembodiment will be described. The program described in the following isexecuted repeatedly in a predetermined period.

At step (hereinafter represented as S) 100, engine ECU 200 detectsengine speed NE based on the signal transmitted from crank positionsensor 306 and detects amount of intake air KL based on the signaltransmitted from air flow meter 314.

At S102, engine ECU 200 detects the vibration intensity of engine 100from a signal transmitted from knock sensor 300. The vibration intensityis represented by a value of voltage output from knock sensor 300. Notethat the vibration intensity may be represented by a value correspondingto the value of the voltage output from knock sensor 300. The vibrationintensity is detected in a combustion stroke for an angle from a topdead center to 90° (a crank angle of 90°).

At S104, engine ECU 200 calculates the 5-degrees integrated value, thatis, integrated value of voltage output from knock sensor 300 (i.e.,representing intensity of vibration), for a crank angle of every fivedegrees (integrated for only 5 degrees). The 5-degrees integrated valueis calculated for the vibration of each of the first to third frequencybands A to C. Further, 5-degrees integrated values of the first to thirdfrequency bands A to C are added in correspondence with the crankangles, and the vibration waveform of engine 100 is detected.

At S110, engine ECU 200 calculates 15-degrees integrated value for eachof the ranges obtained by equally dividing the knock detection gate by6.

At S112, engine ECU 200 detects amounts of change ΔV(1) to ΔV(6) of15-degrees integrated value from the difference between the 15-degreesintegrated value of the present ignition cycle and the 15-degreesintegrated value of the last (one previous) ignition cycle.

At S114, engine ECU 200 specifies two ranges in which the detectedamount of change in 15-degrees integrated value is larger, from the sixranges.

At S116, engine ECU 200 specifies, in the search range determined to bethe same range as the specified range, the crank angle of whichintensity (5-degrees integrated value) is larger than that of aneighboring crank angle and the largest among such intensities.

At S120, engine ECU 200 normalizes the vibration waveform of engine 100.At S122, engine ECU 200 calculates the coefficient of correlation K,which is the value related to the deviation between the normalizedvibration waveform and the knock waveform model. At S124, engine ECU 200calculates the knock intensity N.

At S126, engine ECU 200 determines whether knock intensity N is largerthan the determination value V(J) or not, and whether the coefficient ofcorrelation K is larger than the threshold value K(0) or not. If theknock intensity N is larger than the determination value V(J) and thecoefficient of correlation K is larger than the threshold value K(0)(YES at S126), the process proceeds to S128. If not (NO at S126), theprocess proceeds to S132.

At S128, engine ECU 200 determines that knock has occurred in engine100. At S130, engine ECU 200 retards the ignition timing. At S132,engine ECU 200 determines that knock has not occurred in engine 100. AtS134, engine ECU 200 advances the ignition timing.

An operation of engine ECU 200 as the knock determination deviceaccording to the present embodiment based on the above-describedconfiguration and flowchart will be described.

While engine 100 is in operation, engine speed NE is detected based onthe signal transmitted from crank position sensor 306, and the amount ofintake air KL is detected based on the signal transmitted from air flowmeter 314 (S100). Further, vibration intensity of engine 100 is detectedbased on the signal transmitted from knock sensor 300 (S102).

In a combustion stroke for a range from the top dead center to 90°,5-degrees integrated value for every five degrees is calculated forvibrations of each of the first to third frequency bands A to C (S104).The calculated 5-degrees integrated values of the first to thirdfrequency bands A to C are added in correspondence with the crankangles, and the vibration waveform of engine 100 such as shown in FIG. 4is detected.

Further, as shown in FIG. 9 described above, 15-degrees integrated valueis calculated for each of the ranges obtained by equally dividing theknock detection gate by 6 (S110). Amounts of change ΔV(1) to ΔV(6) of15-degrees integrated value are detected from the difference between the15-degrees integrated value of the present ignition cycle and the15-degrees integrated value of the last (one previous) ignition cycle(S112).

Knocking occurs abruptly and, therefore, it is highly possible that arange in which the amount of change ΔV(1) to ΔV(6) of 15-degreesintegrated value is large includes the crank angle at which knockoccurred. Therefore, two ranges having larger amount of change detectedin 15-degrees integrated value are specified, among the six ranges(S114).

In the search range determined to be the same range as the specifiedrange, the crank angle of which intensity is larger than that of aneighboring crank angle and the largest among such intensities isspecified (S116). In this manner, a crank angle at which knock possiblyhas occurred can be specified.

The vibration waveform is normalized (S120). A timing at which vibrationintensity becomes the highest in the knock waveform model is matchedwith the specified crank angle and, in this state, the absolute valueΔS(I) of the deviation between the normalized vibration waveform and theknock waveform model for each crank angle is calculated. Based on thesum ΣΔS(I) of ΔS(I)s and the value S obtained by integrating vibrationintensity of the knock waveform model for the crank angle, thecoefficient of correlation K is calculated as K=(S−ΣΔS(I))/S (S122). Inthis manner, it becomes possible to have the degree of matching betweenthe detected vibration waveform and the knock waveform model innumerical representation, which allows objective determination. Further,comparison between the vibration waveform and the knock waveform modelallows analysis as to whether the vibration derives from knocking, basedon the vibration behavior such as the attenuation tendency of vibration.

Further, knock intensity N is calculated (S124). If the knock intensityN is larger than the determination value V(J) and the coefficient ofcorrelation K is larger than the threshold value K(0) (YES at S126), itis determined that knock has occurred (S128), and the ignition timing isretarded (S130). This prevents knocking.

If the knock intensity N is not larger than the determination value V(J)or the coefficient of correlation K is not larger than the thresholdvalue K(0) (NO at S126), it is determined that knock has not occurred(S132), and the ignition timing is advanced (S134).

As described above, in engine ECU as the controller in accordance withthe present embodiment, 15-degrees integrated value is calculated foreach of the ranges obtained by equally dividing the knock detection gateby 6. Amounts of change ΔV(1) to ΔV(6) of 15-degrees integrated valueare detected from the difference between the 15-degrees integrated valueof the present ignition cycle and the 15-degrees integrated value of thelast ignition cycle. Two ranges having larger amounts of change detectedin 15-degrees integrated value are specified, among the six ranges. Inthe specified range, the crank angle of which intensity is larger thanthat of a neighboring crank angle and the largest among such intensitiesis specified. In this manner, it is possible to specify a crank anglethat is considered to involve change in vibration intensity betweenignition cycles. Specifically, a crank angle at which knock possibly hasoccurred can be specified. A timing at which vibration intensity becomesthe highest in the knock waveform model is matched with the specifiedcrank angle and, in this state, the coefficient of correlation K iscalculated. Using the coefficient of correlation K, whether knock hasoccurred or not is determined. Consequently, it becomes possible todetermine whether knock has occurred or not based on that portion ofdetected waveform at which the intensity abruptly increased. Therefore,determination as to whether knock has occurred or not based on theportion constantly having high intensity can be avoided. Thus, falsedetermination that knock has occurred when actually there is no knockingcan be avoided.

Second Embodiment

In the following, a second embodiment of the present invention will bedescribed. In the present embodiment, if the crank angle specified asthe crank angle in which the intensity (5-degrees integrated value)peaks is within a prescribed range, determination is made that knock hasnot occurred and, in this point it is different from the firstembodiment. Except for this point, other configurations are the same asthose of the first embodiment described above. Functions are also thesame. Therefore, detailed description thereof will not be repeated.

Referring to FIG. 12, functions of engine ECU 200 as the knockdetermination device in accordance with the present embodiment will bedescribed. The functions of engine ECU 200 described below may beimplemented by hardware or software. The same components as in the firstembodiment above are denoted by the same reference characters anddetailed description thereof will not be repeated here.

Engine ECU 200 additionally includes a determination unit 260.Determination unit 260 determines that knock has not occurred, if thecrank angle specified as having peak intensity exists in a retarded side(larger crank angle) one of two ranges obtained by equally dividing theknock detection gate by two.

In other words, determination unit 260 determines that knock has notoccurred, if the crank angle specified as having peak intensity does notexists in an advanced side (smaller crank angle) one of the two rangesobtained by equally dividing the knock detection gate by two.

The range used for determining that knock has not occurred is notlimited to the range obtained by equally dividing the knock detectiongate by two, and any range in the knock detection gate may be used. Byway of example, a plurality of such ranges, such as the ranges from topdead center to 10° and from 55° to 90° may be set. Further, the rangemay be varied in accordance with the operation condition.

Referring to FIG. 13, control structure of the program executed byengine ECU 200 as the knock determination device in accordance with thepresent embodiment will be described. The same processes as those of thefirst embodiment above are denoted by the same step numbers. Therefore,detailed description thereof will not be repeated.

At S200, engine ECU 200 determines whether or not the specified crankangle is in the retarded side one of the ranges obtained by equallydividing the knock detection gate by two. If the specified crank angleis in the retarded side one of the ranges obtained by equally dividingthe knock detection gate by two (YES at S200), the process proceeds toS132. If not (NO at S200), the process proceeds to S120.

An operation of engine ECU 200 as the knock determination deviceaccording to the present embodiment based on the above-describedconfiguration and flowchart will be described.

As shown by the hatching in FIG. 14, if the amount of change in15-degrees integrated value is large in the range near the crank angleof 90°, that is, near the end point of knock detection gate, the crankangle involving peak intensity can be specified on the retarded side oneof the ranges obtained by equally dividing the knock detection gate bytwo.

It is known that knock occurs near the top dead center in engine 100. Inother words, vibration that occurs near the crank angle of 90° is causednot by knocking.

Therefore, if the range specified as the range in which the amount ofchange in 15-degrees integrated value is larger exists in the retardedside one of the ranges obtained by equally dividing the knock detectiongate by two (YES at S200), it is determined that knock has not occurred(S132).

Therefore, even when vibration intensity increases accidentally at acrank angle at which knocking occurrence is impossible, falsedetermination that knock has occurred when actually there is no knockingcan be avoided. Rather than the determination that knock has notoccurred, the coefficient of correlation K may be calculated to “0”.

Third Embodiment

In the following, the third embodiment of the present invention will bedescribed. In the present embodiment, a range including the rangespecified as having larger amount of change in 15-degrees integratedvalue and wider than the specified range is defined as the search rangeand, in this point, it is different from the first embodiment describedabove. If there is no crank angle in which the intensity peaks in thesearch range, it is determined that knock has not occurred, and in thispoint also, it differs from the first embodiment described above. Exceptfor these points, other configurations are the same as those of thefirst embodiment described above. Functions are also the same.Therefore, detailed description thereof will not be repeated.

As shown in FIG. 15, in the present embodiment, a range including therange specified as having larger amount of change in 15-degreesintegrated value and wider than the specified range is defined as thesearch range. Therefore, it is possible to detect a vibration peak evenfrom the vicinity of a crank angle range in which the amount of changein the integrated value is large. Therefore, even if there is no crankangle in which intensity peaks in the range specified as having largeramount of change in 15-degrees integrated value, it is possible tospecify a crank angle in which the intensity peaks, if such a crankangle exists near the specified range. As a result, peak intensityderived from knocking can be specified with higher accuracy.

Referring to FIG. 16, functions of engine ECU 200 as the knockdetermination device in accordance with the present embodiment will bedescribed. The functions of engine ECU 200 described below may beimplemented by hardware or software. The same components as in the firstembodiment above are denoted by the same reference characters anddetailed description thereof will not be repeated here.

Engine ECU 200 additionally includes a determination unit 262.Determination unit 262 determines that knock has not occurred, if thecrank angle specified as having higher intensity than that of aneighboring crank angle, that is, the crank angle having peak intensity,does not exist in the search range.

Referring to FIG. 17, control structure of the program executed byengine ECU 200 as the knock determination device in accordance with thepresent embodiment will be described. The same processes as those of thefirst embodiment above are denoted by the same step numbers. Therefore,detailed description thereof will not be repeated.

At S300, engine ECU 200 determines whether there is any crank anglehaving higher intensity than that of a neighboring crank angle, that is,the crank angle having peak intensity, in the search range or not. Ifthe crank angle having the peak intensity exists in the search range(YES at S300), the process proceeds to S116. If not (NO at S300), theprocess proceeds to S132.

An operation of engine ECU 200 as the knock determination deviceaccording to the present embodiment based on the above-describedconfiguration and flowchart will be described.

If the crank angle in which the intensity peaks does not exist in thesearch range (YES at S300), it may be the case that vibration intensityaccidentally increased at a crank angle in which knocking is impossible,that is, outside the search range. In this case, it is determined thatknock has not occurred (S132). Therefore, false determination that knockhas occurred when actually there is no knocking can be avoided. Ratherthan the determination that knock has not occurred, the coefficient ofcorrelation K may be calculated to “0”.

Fourth Embodiment

In the following, the fourth embodiment of the present invention will bedescribed. In the present embodiment, the amount of change in the15-degrees integrated value is detected from the absolute value ofdifference between the 15-degrees integrated value of the presentignition cycle and the 15-degrees integrated value of the last ignitioncycle, and in this point it is different from the first embodimentdescribed above. Except for this point, other configurations are thesame as those of the first embodiment described above. Functions arealso the same. Therefore, detailed description thereof will not berepeated.

When the amounts of change ΔV(1) to ΔV(6) in the 15-degrees integratedvalue are detected from the absolute value of difference between the15-degrees integrated value of the present ignition cycle and the15-degrees integrated value of the last ignition cycle, the amounts ofchange ΔV(1) to ΔV(6) in the 15-degrees integrated value can be detectedeven if the intensity of the present ignition cycle is smaller than theintensity of the last ignition cycle, as shown by the hatching in FIG.18.

Fifth Embodiment

In the following the fifth embodiment of the present invention will bedescribed. In the present embodiment, the number of ranges to bespecified as ranges having larger amount of change is determined inaccordance with the ratio of each of the amounts of change ΔV(1) toΔV(6) in the 15-degrees integrated value with respect to the sum ΔV(A)of amounts of change ΔV(1) to ΔV(6) in the 15-degrees integrated valueand, in this point, it is different from the first embodiment describedabove. Except for this point, other configurations are the same as thoseof the first embodiment described above. Functions are also the same.Therefore, detailed description thereof will not be repeated.

Referring to FIG. 19, functions of engine ECU 200 as the knockdetermination device in accordance with the present embodiment will bedescribed. The functions of engine ECU 200 described below may beimplemented by hardware or software. The same components as in the firstembodiment above are denoted by the same reference characters anddetailed description thereof will not be repeated here.

Engine ECU 200 further includes a ratio calculating unit 264 and aspecified number setting unit 266. Ratio calculating unit 264 calculatesthe ratio of each of the amounts of change ΔV(1) to ΔV(6) in the15-degrees integrated value with respect to the sum ΔV(A) of amounts ofchange ΔV(1) to ΔV(6) in the 15-degrees integrated value.

Specified number setting unit 266 determines “1” to be the number ofranges to be specified, if at least one of the ratios of the amounts ofchange ΔV(1) to ΔV(6) in the 15-degrees integrated value with respect tothe sum ΔV(A) of amounts of change ΔV(1) to ΔV(6) in the 15-degreesintegrated value is equal to or higher than a threshold value (forexample, 50%).

The unit determines “2” to be the number of ranges to be specified, ifall of the ratios of the amounts of change ΔV(1) to ΔV(6) in the15-degrees integrated value with respect to the sum ΔV(A) of amounts ofchange ΔV(1) to ΔV(6) in the 15-degrees integrated value are lower thanthe threshold value. The number of the ranges to be specified may beother than “1” or “2”.

Referring to FIG. 20, control structure of the program executed byengine ECU 200 as the knock determination device in accordance with thepresent embodiment will be described. The same processes as those of thefirst embodiment above are denoted by the same step numbers. Therefore,detailed description thereof will not be repeated.

At S500, engine ECU 200 calculates the ratio of each of the amounts ofchange ΔV(1) to ΔV(6) in the 15-degrees integrated value with respect tothe sum ΔV(A) of amounts of change ΔV(1) to ΔV(6) in the 15-degreesintegrated value.

At S502, engine ECU 200 determines whether or not at least one of theratios of the amounts of change ΔV(1) to ΔV(6) in the 15-degreesintegrated value with respect to the sum ΔV(A) of amounts of changeΔV(1) to ΔV(6) in the 15-degrees integrated value is equal to or higherthan a threshold value.

If at least one of the ratios of the amounts of change ΔV(1) to ΔV(6) inthe 15-degrees integrated value with respect to the sum ΔV(A) of amountsof change ΔV(1) to ΔV(6) in the 15-degrees integrated value is equal toor higher than the threshold value (YES at S502), the process proceedsto S504. If not (NO at S502), the process proceeds to S508.

At S504, engine ECU 200 determines “1” to be the number of ranges to bespecified. At S506, engine ECU 200 specifies one range in which thedetected amount of change in the 15-degrees integrated value is large.Specifically, it specifies the range in which the amount of change inthe 15-degrees integrated value is the largest. At S508, engine ECU 200determines “2” to be the number of ranges to be specified.

An operation of engine ECU 200 as the knock determination deviceaccording to the present embodiment based on the above-describedconfiguration and flowchart will be described.

If knock does not occur but vibration is caused by a factor other thanknocking, it is possible as shown in FIG. 21 that the amount of changein 15-degrees integrated value of the range in which knock is impossibleincreases significantly as compared with the amounts of change in15-degrees integrated value of other ranges.

If two ranges are specified as ranges in which amount of change in15-degrees integrated value is large, a range in which relative amountof change is large but absolute amount of change is small would possiblybe specified. Specification of such a range may lead to an erroneousdetermination that knock has occurred.

Therefore, the ratios of the amounts of change ΔV(1) to ΔV(6) in the15-degrees integrated value with respect to the sum ΔV(A) of amounts ofchange ΔV(1) to ΔV(6) in the 15-degrees integrated value are calculated(S500). If any one of the ratios of the amounts of change ΔV(1) to ΔV(6)in the 15-degrees integrated value with respect to the sum ΔV(A) ofamounts of change ΔV(1) to ΔV(6) in the 15-degrees integrated value isequal to or higher than the threshold value (YES at S502), “1” isdetermined to be the number of ranges to be specified (S504).

Therefore, one having the larger amount of change detected in 15-degreesintegrated value among the six ranges is specified (S506). Therefore, itbecomes possible to avoid specification of a range in which relativeamount of change is large but absolute amount of change is small.Accordingly, it is possible to prevent erroneous specification of acrank angle in which the intensity peaks, from a range of lowpossibility that knock has occurred. Therefore, erroneous determinationcan be reduced.

If all the ratios of the amounts of change ΔV(1) to ΔV(6) in the15-degrees integrated value with respect to the sum ΔV(A) of amounts ofchange ΔV(1) to ΔV(6) in the 15-degrees integrated value are lower thanthe threshold value (NO at S502), “2” is specified as the number ofranges to be specified as normally done (S508).

Sixth Embodiment

In the following, the sixth embodiment of the present invention will bedescribed. In the present embodiment, the amounts of change ΔV(1) toΔV(6) in the 15-degrees integrated value are detected based on thedifference from the 15-degrees integrated value of the last or moreprevious ignition cycle that satisfies the condition that intensityvalue LOG(V) is smaller than the knock determination level V(KD) and, inthis point, the present embodiment differs from the first embodiment.Except for this point, other configurations are the same as those of thefirst embodiment described above. Functions are also the same.Therefore, detailed description thereof will not be repeated.

In the present embodiment, the amounts of change ΔV(1) to ΔV(6) in the15-degrees integrated value are detected based on the difference betweenthe 15-degrees integrated values of the present ignition cycle and the15-degrees integrated values of the last or more previous ignition cyclesatisfying the conditions that intensity value LOG(V) is smaller thanthe knock determination level V(KD) shown in the frequency distributionof FIG. 22.

Specifically, If the intensity value LOG(V) of the last ignition cycleis not lower than the knock determination level V(KD) and the intensityvalue LOG(V) of the second last ignition cycle is smaller than the knockdetermination level V(KD), the amounts of change ΔV(1) to ΔV(6) in the15-degrees integrated value are detected based on the difference betweenthe 15-degrees integrated values of the present ignition cycle and the15-degrees integrated values of the second last ignition cycle.

Here, the intensity value LOG(V) is calculated using the maximumintensity of the detected vibration waveform and, therefore, that theintensity value LOG(V) is smaller than the knock determination levelV(KD) is the same that the maximum intensity of detected waveform issmaller than the value obtained by antilogarithmic transformation ofknock determination level V(KD).

Referring to FIG. 23, the control structure of the program executed byengine ECU 200 as the knock determination device in accordance with thepresent embodiment will be described. The same processes as those of thefirst embodiment above are denoted by the same step numbers. Therefore,detailed description thereof will not be repeated.

At S600, engine ECU 200 determines whether the intensity value LOG(V) ofthe last ignition cycle is smaller than the knock determination levelV(KD) or not. If the intensity value LOG(V) of the last ignition cycleis smaller than the knock determination level V(KD) (YES at S600), theprocess proceeds to S1112. If not (NO at S600), the process proceeds toS602.

At S602, engine ECU 200 detects the amounts of change ΔV(1) to ΔV(6) inthe 15-degrees integrated value, based on the difference between the15-degrees integrated values of the present ignition cycle and the15-degrees integrated values of that one the second last or moreprevious ignition cycles which is the latest and having the intensityvalue LOG(V) smaller than the knock determination level V(KD).

It is noted that one of the second last or more previous ignition cycleshaving the intensity value LOG(V) smaller than the knock determinationlevel V(KD) and not the latest ignition cycle may be used.

An operation of engine ECU 200 as the knock determination deviceaccording to the present embodiment based on the above-describedconfiguration and flowchart will be described.

If knock has occurred or vibration of high intensity has occurredbecause of some factor other than knocking in the last ignition cycle,the 15-degrees integration value of the last ignition cycle could belarge. If the amounts of change ΔV(1) to ΔV(6) in the 15-degreesintegrated value are detected based on the 15-degrees integration valueof the ignition cycle as such, the amounts of change themselves becomesmaller even if knock has occurred in the present ignition cycle.

Therefore, if the intensity value LOG(V) of the last ignition cycle islarger than the knock determination level V(KD) (NO at S600), theamounts of change ΔV(1) to ΔV(6) in the 15-degrees integrated value aredetected based on the difference between the 15-degrees integrated valueof the present ignition cycle and the 15-degrees integrated value ofthat one the second last or more previous ignition cycles which is thelatest and having the intensity value LOG(V) smaller than the knockdetermination level V(KD) (S602).

Specifically, the amounts of change ΔV(1) to ΔV(6) in the 15-degreesintegrated value are detected, using the 15-degrees integrated values ofthe ignition cycle free of vibration caused by knocking or vibrationcaused by a factor other than knocking as the reference.

Therefore, a situation where the amounts of change become small despiteof knocking occurrence can be avoided. As a result, a range in whichknocking has possibly been occurred may be specified with high accuracy.

If the intensity value LOG(V) of the last ignition cycle is smaller thanthe knock determination level V(KD) (YES at S600), the amounts of changeΔV(1) to ΔV(6) in the 15-degrees integrated value are detected based onthe difference between the 15-degrees integrated values of the presentignition cycle and the 15-degrees integrated values of the last(immediately preceding) ignition cycle (S112).

Seventh Embodiment

In the following, the seventh embodiment of the present invention willbe described. In the present embodiment, the amounts of change ΔV(1) toΔV(6) in the 15-degrees integrated value are detected based on thedifference from the 15-degrees integrated value of a plurality of lastand more previous ignition cycles that continuously satisfy for morethan a predetermined number of times the condition that the intensityvalue LOG(V) is larger than the knock determination level V(KD) and, inthis point, the present embodiment differs from the sixth embodiment.Except for this point, other configurations are the same as those of thefirst and sixth embodiments described above. Functions are also thesame. Therefore, detailed description thereof will not be repeated.

Referring to FIG. 24, the control structure of the program executed byengine ECU 200 as the knock determination device in accordance with thepresent embodiment will be described. The same processes as those of thefirst or sixth embodiment above are denoted by the same step numbers.Therefore, detailed description thereof will not be repeated.

At S700, engine ECU 200 determines whether ignition cycles having theintensity value LOG(V) larger than the knock determination level V(KD)had continued for a predetermined number of times or more until the lastignition cycle. If the ignition cycles having the intensity value LOG(V)larger than the knock determination level V(KD) had continued for apredetermined number of times or more (YES at S700), the processproceeds to S112. If not (NO at S700), the process proceeds to S602.

An operation of engine ECU 200 as the knock determination deviceaccording to the present embodiment based on the above-describedconfiguration and flowchart will be described.

If the intensity value LOG(V) of the last ignition cycle is larger thanthe knock determination level V(KD) (NO at S600), whether or notignition cycles having the intensity value LOG(V) larger than the knockdetermination level V(KD) had continued for a predetermined number oftimes or more until the last ignition cycle is determined (S700).

If ignition cycles having the intensity value LOG(V) larger than theknock determination level V(KD) had continued for a predetermined numberof times or more (YES at S700), it is considered that vibration of highintensity is not an abrupt vibration caused by knocking or the like butconstant vibration generated in engine 100 itself.

In this case, the amounts of change ΔV(1) to ΔV(6) in the 15-degreesintegrated value are detected based on the difference between the15-degrees integrated values of the present ignition cycle and the15-degrees integrated values of the last (immediately preceding)ignition cycle (S112), as is normally done. Thus, it becomes possible todetermine whether knock has occurred or not based on the vibrationgenerated constantly in engine 100. Therefore, false determination thatknock has occurred when actually there is no knocking can be avoided.

If ignition cycles having the intensity value LOG(V) larger than theknock determination level V(KD) had not continued for a predeterminednumber of times or more (NO at S700), it is considered that thevibration of high intensity corresponds to a vibration abruptly occurredbecause of knocking or the like.

In this case, the amounts of change ΔV(1) to ΔV(6) in the 15-degreesintegrated value are detected based on the difference between the15-degrees integrated values of the present ignition cycle and the15-degrees integrated values of that one the second last or moreprevious ignition cycles which is the latest and having the intensityvalue LOG(V) smaller than the knock determination level V(KD) (S602).

Specifically, the amounts of change ΔV(1) to ΔV(6) in the 15-degreesintegrated value are detected, using as the reference the 15-degreesintegrated value of the ignition cycle free of vibration caused byknocking or vibration of high intensity caused by a factor other thanknocking.

Therefore, a situation where the amounts of change become small despiteof knocking occurrence can be avoided. As a result, a range in whichknock has possibly been occurred may be specified with high accuracy.

If ignition cycles having the intensity value LOG(V) larger than theknock determination level V(KD) had continued for a predetermined numberof times or more until the last ignition cycle, the 15-degreesintegrated value of any of the plurality of ignition cycles continuouslysatisfying, for a predetermined number or larger times, the conditionthat the intensity value LOG(V) is larger than the knock determinationlevel V(KD) may be used, in place of the last ignition cycle.

Eighth Embodiment

In the following, the eighth embodiment of the present invention will bedescribed. In the present embodiment, the amounts of change ΔV(1) toΔV(6) in the 15-degrees integrated value are detected based on thedifference between the 15-degrees integrated value of the presentignition cycle and the operation value calculated from past 15-degreesintegrated value using a method of smoothing referred to as exponentialsmoothing, that is, the operation value obtained by smoothing the15-degrees integrated value and, in this the point, the presentembodiment differs from the first embodiment. Except for this point,other configurations are the same as those of the first embodimentdescribed above. Functions are also the same. Therefore, detaileddescription thereof will not be repeated.

Referring to FIG. 25, functions of an engine ECU 200 as the knockdetermination device in accordance with the present embodiment will bedescribed. The functions of engine ECU 200 described below may beimplemented by hardware or software. The same components as in the firstembodiment above are denoted by the same reference characters anddetailed description thereof will not be repeated here.

Engine ECU 200 additionally includes an operation value calculating unit268. Operation value calculating unit 268 calculates an operation value(smoothed 15-degrees integrated value) VN in accordance with Equation(1) below. In Equation (1), VN(i) represents the operation value VNcalculated in the present ignition cycle. VN(i−1) represents theoperation value calculated in the last ignition cycle. V15(i−1)represents 15-degrees integrated value of the last ignition cycle. Z isa constant.VN(i)=VN(i−1)+Z×(V15(i−1)−VN(i−1)  (1)

The operation value VN is calculated for each of the plurality of crankangle ranges.

Referring to FIG. 26, the control structure of the program executed byengine ECU 200 as the knock determination device in accordance with thepresent embodiment will be described. The same processes as those of thefirst embodiment above are denoted by the same step numbers. Therefore,detailed description thereof will not be repeated.

At S800, engine ECU 200 calculates the operation value VN from15-degrees integrated value through exponential smoothing.

At S802, engine ECU 200 detects the amounts of change ΔV(1) to ΔV(6) inthe 15-degrees integrated value based on the difference between the15-degrees integrated value of the present ignition cycle and theoperation value VN.

In this manner, it is possible to detect the amounts of change ΔV(1) toΔV(6) in the 15-degrees integrated value using the operation value VNthat not much vary ignition cycle by ignition cycle as a reference.Therefore, it becomes possible to determine whether knock has occurredor not stably with high accuracy. The method of smoothing is not limitedto the one described above and it may be realized by using simple movingaverage or a filter.

Ninth Embodiment

In the following, the ninth embodiment of the present invention will bedescribed. In the present embodiment, the operation value VN iscalculated using the 15-degrees integrated values of only those ignitioncycles which satisfy the condition that the intensity value LOG(V) issmaller than the knock determination level V(KD) and, in this point, thepresent embodiment differs from the first embodiment. Except for thispoint, other configurations are the same as those of the first andeighth embodiments described above. Functions are also the same.Therefore, detailed description thereof will not be repeated.

Referring to FIG. 27, the control structure of the program executed byengine ECU 200 as the knock determination device in accordance with thepresent embodiment will be described. The same processes as those of thefirst or ninth embodiment above are denoted by the same step numbers.Therefore, detailed description thereof will not be repeated.

At S900, engine ECU 200 determines whether the intensity value LOG(V)was smaller than the knock determination level V(KD) in the lastignition cycle or not. If the intensity value LOG(V) is smaller than theknock determination level V(KD) in the last ignition cycle (YES atS900), the process proceeds to S800. If not (NO at S900), the processproceeds to S802.

In this manner, it becomes possible to calculate the operation value VNfrom the 15-degrees integrated values excluding the 15-degreesintegrated value of the ignition cycle in which knock occurred. Theamounts of change ΔV(1) to ΔV(6) in the 15-degrees integrated value aredetected using as a reference the operation value VN as such. Therefore,it is possible to detect amounts of change ΔV(1) to ΔV(6) in the15-degrees integrated value using the operation value VN that not muchvary by ignition cycle as a reference. Therefore, it becomes possible todetermine whether knock has occurred or not stably with high accuracy.

Tenth Embodiment

In the following, the tenth embodiment of the present invention will bedescribed. In the present embodiment, if the coefficient of correlationK is not larger than the threshold value K(0), or if the crank anglespecified as the crank angle having peak intensity exists in a retardedside (larger crank angle) one of two ranges obtained by equally dividingthe knock detection gate by two, the detected vibration waveform iscorrected. In this point, it is different from the first embodimentdescribed above.

Further, in the present embodiment, the intensity value LOG(V) used forthe frequency distribution shown in FIG. 28 is calculated by logarithmictransformation of a value obtained by integrating intensities from thetop dead center to 90° in a combustion stroke (hereinafter also referredto as a 90-degrees integrated value). Further, in the presentembodiment, knock intensity N is calculated by dividing the 90-degreesintegrated value by BGL. Specifically, in the present embodiment, using90-degrees integrated value in place of 5-degrees integrated value, thefrequency distribution is formed and the knock intensity is calculated.

Except for these points, structure of engine 100 itself and the like arethe same as those of the first embodiment. Functions are also the same.Therefore, detailed description thereof will not be repeated.

Referring to FIG. 29, functions of an engine ECU 200 as the knockdetermination device in accordance with the present embodiment will bedescribed. The functions of engine ECU 200 described below may beimplemented by hardware or software. The same components as in the firstembodiment above are denoted by the same reference characters anddetailed description thereof will not be repeated here.

Engine ECU 200 additionally includes a determining unit 270, acorrecting unit 272, an integrated value calculating unit 274, anupdating unit 276, and an inhibiting unit 278. Determining unit 270determines whether the 15-degrees integrated value of the rangespecified as the crank angle range having large amount of change in15-degrees integrated value has changed by a factor other than knockingor not. Specifically, if the change is caused by mechanical vibrationderived from an operation of components (intake valve 116, exhaust valve118 or the like) of engine 100 itself or not is determined.

By way of example, if the coefficient of correlation K is not largerthan the threshold value K(0), or if the crank angle specified as thecrank angle having peak intensity exists in a retarded side (largercrank angle) one of two ranges obtained by equally dividing the knockdetection gate by two, it is determined that the 15-degrees integratedvalue has changed not because of knocking.

On the contrary, if the coefficient of correlation K is larger than thethreshold value K(0), or if the crank angle specified as the crank anglehaving peak intensity exists in an advanced side (larger crank angle)one of two ranges obtained by equally dividing the knock detection gateby two, it is determined that the 15-degrees integrated value haschanged because of knocking.

Whether the 15-degrees integrated value has changed because of knockingor not is determined for each of the plurality of (in the presentembodiment, two) ranges specified as the crank angle ranges having largeamount of change in 15-degrees integrated value. Therefore, a pluralityof (in the present embodiment, two) coefficients of correlation K arecalculated using respective crank angles specified as crank angles withpeak intensity. The method of calculating the coefficient of correlationK is the same as in the first embodiment described above and, therefore,detailed description thereof will not be repeated.

The method of determining whether the 15-degrees integrated value haschanged because of knocking or not is not limited to the one describedabove. Further, if the crank angle specified as the crank angle havingpeak intensity exists in a retarded side (larger crank angle) one of tworanges obtained by equally dividing the knock detection gate by two, thecoefficient of correlation K may be calculated as “0”.

Correcting unit 272 corrects the detected vibration waveform such thatthe amount of change in 15-degrees integrated value of the range inwhich 15-degrees integrated value is determined to have changed notbecause of knocking becomes smaller. More specifically, the 15-degreesintegrated value is adjusted to be equal to the 15-degrees integratedvalue calculated in the last ignition cycle.

Integrated value calculating unit 274 calculates the 15-degreesintegrated value and the 90-degrees integrated value of the intensity inthe corrected vibration waveform. Updating unit 276 updates frequencydistribution of intensity value LOG(V), using the 90-degrees integratedvalue. By updating the frequency distribution, calculation of BGL,calculation of knock determination level V(KD) and correction ofdetermination value V(J) are executed.

Inhibiting unit 278 inhibits correction of vibration waveform if the15-degrees integrated value of at least one of the plurality of rangesspecified as crank angle ranges having large amount of change in15-degrees integrated value is determined to be derived from knocking.Specifically, correction of vibration waveform is inhibited in allranges.

Referring to FIGS. 30 and 31, the control structure of the programexecuted by engine ECU 200 as the knock determination device inaccordance with the present embodiment will be described. The sameprocesses as those of the first embodiment above are denoted by the samestep numbers. Therefore, detailed description thereof will not berepeated.

At S1000, engine ECU 200 determines whether or not the 15-degreesintegrated values of all the ranges specified as ranges of large15-degrees integrated values have changed because of a factor other thanknocking. If 15-degrees integrated values have changed because of afactor other than knocking in all the ranges (YES at S1000), the processproceeds to S1010. If not (NO at S1000), the process proceeds to S1002.At S1002, engine ECU 200 inhibits correction of vibration waveform.

At S1010, engine ECU 200 determines whether the amount of change of15-degrees integrated value (present 15-degrees integrated value—last15-degrees integrated value) in the range specified as the range oflarge 15-degrees integrated value is a positive value or not. If theamount of change is positive (YES at S1010), the process proceeds toS1012. If not (NO at S1010), the process proceeds to S1020.

At S1012, engine ECU 200 corrects the detected vibration waveform. AtS1014, engine ECU 200 calculates the 15-degrees integrated value of thecorrected vibration waveform. At S1016, engine ECU 200 calculates thesum of 15-degrees integrated values of the corrected vibration waveform,that is, 90-degrees integrated value of the corrected vibrationwaveform.

At S1018, engine ECU 200 updates the frequency distribution of intensityvalue LOG(V), using the 90-degrees integrated value of correctedvibration waveform. By updating the frequency distribution, calculationof BGL, calculation of knock determination level V(KD) and correction ofdetermination value V(J) are executed.

At S1020, engine ECU 200 calculates the 90-degrees integrated value ofthe uncorrected vibration waveform. At S1022, engine ECU 200 updatesfrequency distribution of intensity value LOG(V), using the 90-degreesintegrated value calculated without correcting the vibration waveform.

At S1030, engine ECU 200 determines whether knock intensity N is largerthan the determination value V(J) or not. If the knock intensity N islarger than the determination value V(J) (YES at S1040), the processproceeds to step S128. If not (NO at S1040), the process proceeds toS132.

An operation of engine ECU 200 as the knock determination deviceaccording to the present embodiment based on the above-describedconfiguration and flowchart will be described.

As shown by hatching in FIG. 32, if the amount of change in 15-degreesintegrated value is large in the range near the end point of knockdetection gate, that is, near the crank angle of 90 degrees, the crankangle in which the intensity peaks can be specified from the retardedside one of two ranges obtained by equally dividing the knock detectiongate by two.

It is known that knock occurs near the top dead center in engine 100. Inother words, vibration that occurs near the crank angle of 90° is causednot by knocking.

Therefore, if the range specified as the range in which the amount ofchange in 15-degrees integrated value is larger exists in the retardedside one of the ranges obtained by equally dividing the knock detectiongate by two, it is determined that 15-degrees integrated value haschanged not because of knocking. If the calculated coefficient ofcorrelation K is not higher than the threshold value K(0), it isdetermined that 15-degrees integrated value has changed not because ofknocking. Here, it is assumed that 15-degrees integrated value isdetermined to have changed not because of knocking in each of thespecified ranges (YES at S1000).

If the amount of change in 15-degrees integrated value is positive (YESat S1010), the vibration waveform is corrected such that the 15-degreesintegrated value in the specified range becomes equal to the 15-degreesintegrated value calculated in the last ignition cycle (S1012).Specifically, the hatched portion in FIG. 32 is removed. As a result, awaveform such as shown in FIG. 33 is obtained.

The 15-degrees integrated value of the corrected waveform is calculated(S1014). Further, 90-degrees integrated value of the corrected vibrationwaveform is calculated (S1016). Using the 90-degrees integrated value,frequency distribution of intensity value LOG(V) is updated (S1018). Byupdating the frequency distribution, calculation of BGL, calculation ofknock determination level V(KD) and correction of determination valueV(J) are executed.

In this manner, if a mechanical vibration of high intensity occursabruptly, it is possible to determine whether knock has occurred or notusing the vibration waveform with the intensity of such a vibrationremoved. Therefore, whether knock has occurred or not can be determinedusing the vibration waveform not much influenced by the intensityincreased not because of knocking. As a result, erroneous determinationas to whether knock has occurred or not can be reduced.

On the contrary, if the 15-degrees integrated value of at least one ofthe plurality of ranges specified as crank angle ranges in which theamount of change in 15-degrees integrated value is large is determinedto have changed because of knocking, correction of vibration waveform isinhibited (S1002).

Further, 90-degrees integrated value of the uncorrected vibrationwaveform is calculated (S1020). Using the 90-degrees integrated valuecalculated without correcting vibration waveform, the frequencydistribution of intensity value LOG(V) is updated (S1022).

Further, knock intensity N is calculated (S1124). If knock intensity Nis larger than the determination value V(J) (YES at S1030), it isdetermined that knock has occurred (S128), and the ignition timing isretarded (S130). If the knock intensity N is not larger than thedetermination value V(J) (NO at S1030), it is determined that knock hasnot occurred (S132), and the ignition timing is advanced (S134).

As described above, in engine ECU 1000 as the controller in accordancewith the present embodiment, if it is determined that 15-degreesintegrated value has changed not because of knocking, the detectedvibration waveform is corrected such that the amount of change in15-degrees integrated value becomes smaller. Using the 90-degreesintegrated value of the corrected vibration waveform, frequencydistribution of intensity value LOG(V) is updated. Therefore, if amechanical vibration of high intensity occurs abruptly, it is possibleto determine whether knock has occurred or not using the vibrationwaveform with the intensity of such a vibration removed. Therefore,whether knock has occurred or not can be determined using the vibrationwaveform not much influenced by the intensity increased not because ofknocking. As a result, erroneous determination as to whether knock hasoccurred or not can be reduced.

In place of the difference between the 15-degrees integrated value ofthe present ignition cycle and the 15-degrees integrated value of thelast ignition cycle, an absolute value of the difference between the15-degrees integrated value of the present ignition cycle and the15-degrees integrated value of the last ignition cycle may be used asthe amount of change in 15-degrees integrated value.

As in the eighth embodiment described above, the difference or theabsolute value of difference between the 15-degrees integrated value ofthe present ignition cycle and the operation value obtained from thepast 15-degrees integrated value using smoothing method such asexponential smoothing, simple moving average or a filter (low passfilter), that is, the operation value obtained by smoothing the15-degrees integrated value, may be detected as the amount of change in15-degrees integrated value. In such a case, the detected vibrationwaveform may be corrected such that the 15-degrees integrated value ofthe range in which the 15-degrees integrated value is determined to havechanged not because of knocking comes to have the same value as thesmoothed operation value.

Further, even when it is determined that 15-degrees integrated value ofat least one of the plurality of ranges specified as the crank angleranges having large amount of change in 15-degrees integrated value haschanged because of knocking, the vibration waveform may be corrected ina range in which 15-degrees integrated value is determined to havechanged not because of knocking.

Other Embodiments

The first to tenth embodiments described above may be used in arbitrarycombination.

The embodiments as have been described here are mere examples and shouldnot be interpreted as restrictive. The scope of the present invention isdetermined by each of the claims with appropriate consideration of thewritten description of the embodiments and embraces modifications withinthe meaning of, and equivalent to, the languages in the claims.

1. A knock determination device for an internal combustion engine,comprising: a knock sensor detecting intensity of vibration of saidinternal combustion engine; and an operation unit; wherein saidoperation unit detects a waveform of vibration of said internalcombustion engine based on the detected intensity, calculates, for eachof a predetermined plurality of crank angle ranges, an integrated valueintegrating the vibration intensity of said waveform, detects an amountof change in said integrated value between ignition cycles, based on adifference between said integrated value and a predetermined value,specifies a predetermined number of crank angle ranges in which theamount of change in said integrated value is larger, among saidplurality of crank angle ranges, specifies a crank angle having anintensity higher than the intensity in a neighboring crank angle, in asearch range determined with reference to a specified crank angle range,and while a timing at which intensity becomes the highest in a waveformmodel defined as a reference of vibration in said internal combustionengine is matched with the specified crank angle, based on a result ofcomparison between the waveform and the waveform model in this state,determines whether knock has occurred in the internal combustion engineor not.
 2. The knock determination device for an internal combustionengine according to claim 1, wherein said operation unit determines thatknock has not occurred in said internal combustion engine if saidspecified crank angle is in a predetermined range.
 3. The knockdetermination device for an internal combustion engine according toclaim 1, wherein a range same as said specified crank angle range isdetermined to be said search range.
 4. The knock determination devicefor an internal combustion engine according to claim 1, wherein a rangeincluding said specified crank angle range and wider than said specifiedcrank angle range is determined to be said search range.
 5. The knockdetermination device for an internal combustion engine according toclaim 4, wherein said operation unit determines that knock has notoccurred in said internal combustion engine if a crank angle havinghigher intensity than a neighboring crank angle does not exist in saidsearch range.
 6. The knock determination device for an internalcombustion engine according to claim 1, wherein said operation unitdetects the amount of change in said integrated value between ignitioncycles, based on an absolute value of difference between said integratedvalue and said predetermined value.
 7. The knock determination devicefor an internal combustion engine according to claim 1, wherein saidoperation unit calculates ratio of the amount of change of saidintegrated value with respect to a sum of amounts of change in saidintegrated value; and a number corresponding to the calculated ratio isdetermined to be said predetermined number.
 8. The knock determinationdevice for an internal combustion engine according to claim 7, whereinif at least one of said ratios is larger than a predetermined ratio, 1is determined to be said predetermined number.
 9. The knockdetermination device for an internal combustion engine according toclaim 1, wherein vibration intensity and said waveform of said internalcombustion engine are detected in a plurality of ignition cycles; saidintegrated value is calculated for each ignition cycle; and saidpredetermined value is an integrated value of an ignition cyclepreceding the ignition cycle in which the waveform to be compared withsaid waveform model is detected.
 10. The knock determination device foran internal combustion engine according to claim 9, wherein saidpredetermined value is an integrated value of an ignition cyclepreceding the ignition cycle in which the waveform to be compared withsaid waveform model is detected and satisfying a condition that maximumvibration intensity is smaller than a predetermined intensity.
 11. Theknock determination device for an internal combustion engine accordingto claim 9, wherein said predetermined value is an integrated value ofan ignition cycle preceding the ignition cycle in which the waveform tobe compared with said waveform model is detected and being any one of aplurality of ignition cycles continuously satisfying, for more than apredetermined number of times, the condition that maximum vibrationintensity is larger than a predetermined intensity.
 12. The knockdetermination device for an internal combustion engine according toclaim 1, wherein said predetermined value is an operation value obtainedby smoothing said integrated value.
 13. The knock determination devicefor an internal combustion engine according to claim 12, wherein saidpredetermined value is an operation value obtained by smoothing saidintegrated value in an ignition cycle of which maximum vibrationintensity is smaller than a predetermined intensity.
 14. The knockdetermination device for an internal combustion engine according toclaim 1, wherein said operation unit calculates a value corresponding toa difference between said waveform and said waveform model such that thevalue becomes larger as the difference between said waveform and saidwaveform model becomes smaller, and when the value corresponding to thedifference becomes larger than a threshold value, determines that knockhas occurred.
 15. A knock determination method for an internalcombustion engine, comprising the steps of: detecting intensity ofvibration of said internal combustion engine; detecting waveform ofvibration of said internal combustion engine based on the detectedintensity; calculating, for each of a predetermined plurality of crankangle ranges, an integrated value integrating the vibration intensity ofsaid waveform; detecting an amount of change in said integrated valuebetween ignition cycles, based on a difference between said integratedvalue and a predetermined value; specifying a predetermined number ofcrank angle ranges in which the amount of change in said integratedvalue is larger, among said plurality of crank angle ranges; specifyinga crank angle having an intensity higher than the intensity in aneighboring crank angle, in a search range determined with reference toa specified crank angle range; and while a timing at which intensitybecomes the highest in a waveform model defined as a reference ofvibration in said internal combustion engine is matched with thespecified crank angle, based on a result of comparison between thewaveform and the waveform model in this state, determining whether knockhas occurred in the internal combustion engine or not.
 16. The knockdetermination method for an internal combustion engine according toclaim 15, further comprising the step of determining that knock has notoccurred in said internal combustion engine, if said specified crankangle is in a predetermined range.
 17. The knock determination methodfor an internal combustion engine according to claim 15, wherein a rangesame as said specified crank angle range is determined to be said searchrange.
 18. The knock determination method for an internal combustionengine according to claim 15, wherein a range including said specifiedcrank angle range and wider than said specified crank angle range isdetermined to be said search range.
 19. The knock determination methodfor an internal combustion engine according to claim 18, furthercomprising the step of determining that knock has not occurred in saidinternal combustion engine, if a crank angle having higher intensitythan a neighboring crank angle does not exist in said search range. 20.The knock determination method for an internal combustion engineaccording to claim 15, wherein said step of detecting amount of changein said integrated value includes the step of detecting the amount ofchange in said integrated value between ignition cycles, based on anabsolute value of difference between said integrated value and saidpredetermined value.
 21. The knock determination method for an internalcombustion engine according to claim 15, further comprising the step ofcalculating ratio of the amount of change of said integrated value withrespect to a sum of amounts of change in said integrated value; whereina number corresponding to the calculated ratio is determined to be saidpredetermined number.
 22. The knock determination method for an internalcombustion engine according to claim 21, wherein if at least one of saidratios is larger than a predetermined ratio, 1 is determined to be saidpredetermined number.
 23. The knock determination method for an internalcombustion engine according to claim 15, wherein vibration intensity andsaid waveform of said internal combustion engine are detected in aplurality of ignition cycles; said integrated value is calculated foreach ignition cycle; and said predetermined value is an integrated valueof an ignition cycle preceding the ignition cycle in which the waveformto be compared with said waveform model is detected.
 24. The knockdetermination method for an internal combustion engine according toclaim 23, wherein said predetermined value is an integrated value of anignition cycle preceding the ignition cycle in which the waveform to becompared with said waveform model is detected and satisfying a conditionthat maximum vibration intensity is smaller than a predeterminedintensity.
 25. The knock determination method for an internal combustionengine according to claim 23, wherein said predetermined value is anintegrated value of an ignition cycle preceding the ignition cycle inwhich the waveform to be compared with said waveform model is detectedand being any one of a plurality of ignition cycles continuouslysatisfying, for more than a predetermined number of times, the conditionthat maximum vibration intensity is larger than a predeterminedintensity.
 26. The knock determination method for an internal combustionengine according to claim 15, wherein said predetermined value is anoperation value obtained by smoothing said integrated value.
 27. Theknock determination method for an internal combustion engine accordingto claim 26, wherein said predetermined value is an operation valueobtained by smoothing said integrated value in an ignition cycle ofwhich maximum vibration intensity is smaller than a predeterminedintensity.
 28. The knock determination method for an internal combustionengine according to claim 15, further comprising the step of calculatinga value corresponding to a difference between said waveform and saidwaveform model such that the value becomes larger as the differencebetween said waveform and said waveform model becomes smaller; whereinsaid step of determining whether knock occurred or not includes the stepof determining, when the value corresponding to the difference becomeslarger than a threshold value, that knock has occurred.
 29. A knockdetermination device for an internal combustion engine, comprising:means for detecting intensity of vibration of said internal combustionengine; means for detecting waveform of vibration of said internalcombustion engine based on the detected intensity; means forcalculating, for each of a predetermined plurality of crank angleranges, an integrated value integrating the vibration intensity of saidwaveform; detecting means for detecting an amount of change in saidintegrated value between ignition cycles, based on a difference betweensaid integrated value and a predetermined value; first specifying meansfor specifying a predetermined number of crank angle ranges in which theamount of change in said integrated value is larger, among saidplurality of crank angle ranges; second specifying means for specifyinga crank angle having an intensity higher than the intensity in aneighboring crank angle, in a search range determined with reference toa specified crank angle range; and determining means for determining,while a timing at which intensity becomes the highest in a waveformmodel defined as a reference of vibration in said internal combustionengine is matched with the specified crank angle, based on a result ofcomparison between the waveform and the waveform model in this state,whether knock has occurred in the internal combustion engine or not. 30.The knock determination device for an internal combustion engineaccording to claim 29, further comprising means for determining thatknock has not occurred in said internal combustion engine, if saidspecified crank angle is in a predetermined range.
 31. The knockdetermination device for an internal combustion engine according toclaim 29, wherein a range same as said specified crank angle range isdetermined to be said search range.
 32. The knock determination devicefor an internal combustion engine according to claim 29, wherein a rangeincluding said specified crank angle range and wider than said specifiedcrank angle range is determined to be said search range.
 33. The knockdetermination device for an internal combustion engine according toclaim 32, further comprising means for determining that knock has notoccurred in said internal combustion engine if a crank angle havinghigher intensity than a neighboring crank angle does not exist in saidsearch range.
 34. The knock determination device for an internalcombustion engine according to claim 29, wherein said detecting meansincludes means for detecting the amount of change in said integratedvalue between ignition cycles, based on an absolute value of differencebetween said integrated value and said predetermined value.
 35. Theknock determination device for an internal combustion engine accordingto claim 29, further comprising means for calculating ratio of theamount of change of said integrated value with respect to a sum ofamounts of change in said integrated value; wherein a numbercorresponding to the calculated ratio is determined to be saidpredetermined number.
 36. The knock determination device for an internalcombustion engine according to claim 35, wherein if at least one of saidratios is larger than a predetermined ratio, I is determined to be saidpredetermined number.
 37. The knock determination device for an internalcombustion engine according to claim 29, wherein vibration intensity andsaid waveform of said internal combustion engine are detected in aplurality of ignition cycles; said integrated value is calculated foreach ignition cycle; and said predetermined value is an integrated valueof an ignition cycle preceding the ignition cycle in which the waveformto be compared with said waveform model is detected.
 38. The knockdetermination device for an internal combustion engine according toclaim 37, wherein said predetermined value is an integrated value of anignition cycle preceding the ignition cycle in which the waveform to becompared with said waveform model is detected and satisfying a conditionthat maximum vibration intensity is smaller than a predeterminedintensity.
 39. The knock determination device for an internal combustionengine according to claim 37, wherein said predetermined value is anintegrated value of an ignition cycle preceding the ignition cycle inwhich the waveform to be compared with said waveform model is detectedand being any one of a plurality of ignition cycles continuouslysatisfying, for more than a predetermined number of times, the conditionthat maximum vibration intensity is larger than a predeterminedintensity.
 40. The knock determination device for an internal combustionengine according to claim 29, wherein said predetermined value is anoperation value obtained by smoothing said integrated value.
 41. Theknock determination device for an internal combustion engine accordingto claim 40, wherein said predetermined value is an operation valueobtained by smoothing said integrated value in an ignition cycle ofwhich maximum vibration intensity is smaller than a predeterminedintensity.
 42. The knock determination device for an internal combustionengine according to claim 29, further comprising means for calculating avalue corresponding to a difference between said waveform and saidwaveform model such that the value becomes larger as the differencebetween said waveform and said waveform model becomes smaller; whereinsaid determining means includes means for determining, when the valuecorresponding to the difference becomes larger than a threshold value,that knock has occurred.
 43. A knock determination device for aninternal combustion engine, comprising: a knock sensor detectingintensity of vibration of said internal combustion engine; and anoperation unit; wherein said operation unit detects a waveform ofvibration of said internal combustion engine based on the detectedintensity, calculates, for each of a predetermined plurality of crankangle ranges, an integrated value integrating the vibration intensity ofsaid waveform, detects an amount of change in said integrated valuebetween ignition cycles for each of said plurality of crank angleranges, specifies a predetermined number of crank angle ranges in whichthe amount of change in said integrated value is larger, among saidplurality of crank angle ranges, determines whether the integrated valuein said specified range has changed not because of knocking, if it isdetermined that the integrated value in said specified range has changednot because of knocking, corrects said detected vibration waveform suchthat amount of change in the integrated value in said specified rangebecomes smaller, calculates for each of said plurality of crank angleranges, an integrated value integrating vibration intensities of saidcorrected waveform, and determines whether knock has occurred or notusing a sum of each of said integrated values of said correctedwaveform.
 44. The knock determination device for an internal combustionengine according to claim 43, wherein if it is determined that theintegrated value in said specified range has changed not because ofknocking, said operation unit corrects said detected vibration waveformsuch that the integrated value of said specified range becomes equal toan integrated value calculated in the last ignition cycle, so that theamount of change of said integrated value becomes smaller.
 45. The knockdetermination device for an internal combustion engine according toclaim 44, wherein said operation unit detects the amount of change ofsaid integrated value based on a difference of said integrated values ofcontinuous ignition cycles.
 46. The knock determination device for aninternal combustion engine according to claim 44, wherein said operationunit detects the amount of change of said integrated value based on anabsolute value of difference of said integrated values of continuousignition cycles.
 47. The knock determination device for an internalcombustion engine according to claim 43, wherein said operation unitcalculates an operation value by smoothing said integrated value foreach of said plurality of crank angle ranges, and if it is determinedthat the integrated value in said specified range has changed notbecause of knocking, corrects said detected vibration waveform such thatthe integrated value of said specified range becomes equal to saidoperation value, so that the amount of change of said integrated valuebecomes smaller.
 48. The knock determination device for an internalcombustion engine according to claim 47, wherein said operation unitdetects the amount of change of said integrated value based on adifference between said integrated value and said operation value. 49.The knock determination device for an internal combustion engineaccording to claim 47, wherein said operation unit detects the amount ofchange of said integrated value based on an absolute value of differencebetween said integrated value and said operation value.
 50. The knockdetermination device for an internal combustion engine according toclaim 43, wherein said operation unit specifies a crank angle having anintensity higher than the intensity of a neighboring crank angle, in asearch range determined with reference to said specified range, andwhile a timing at which intensity becomes the highest in a waveformmodel defined as a reference of vibration in said internal combustionengine is matched with the specified crank angle, based on a result ofcomparison between the waveform and the waveform model in this state,determines whether the integrated value in said specified range haschanged not because of knocking.
 51. The knock determination device foran internal combustion engine according to claim 50, wherein saidoperation unit calculates a coefficient corresponding to a differencebetween said waveform and said waveform model such that the coefficientbecomes larger as the difference between said waveform and said waveformmodel becomes smaller, and determines, if said coefficient is largerthan a threshold value, that the integrated value in the specified rangehas changed because of knocking, and determines, if said coefficient issmaller than the threshold, that the integrated value in the specifiedrange has changed not because of knocking.
 52. The knock determinationdevice for an internal combustion engine according to claim 43, whereinsaid operation unit determines, if said specified crank angle is in apredetermined range, that the integrated value in said specified rangehas changed not because of knocking.
 53. The knock determination devicefor an internal combustion engine according to claim 43, wherein saidoperation unit specifies a plurality of crank angle ranges in which theamount of change in said integrated value is larger, among saidplurality of crank angle ranges, and said operation unit determineswhether the integrated values in said plurality of specified ranges havechanged not because of knocking.
 54. The knock determination device foran internal combustion engine according to claim 53, wherein if it isdetermined that the integrated value in at least one of said pluralityof specified ranges has changed because of knocking, said operation unitinhibits correction of said detected waveform.
 55. The knockdetermination device for an internal combustion engine according toclaim 53, wherein if it is determined that the integrated value in atleast one of said plurality of specified ranges has changed not becauseof knocking, said operation unit corrects said detected vibrationwaveform such that the amount of change in the integrated value in therange in which said integrated value is determined to have changed notbecause of knocking becomes smaller.
 56. The knock determination devicefor an internal combustion engine according to claim 43, wherein saidoperation unit corrects a determination value used for determiningwhether knock has occurred or not, using a sum of said integrated valuesof said corrected waveform, and determines whether knock has occurred ornot based on a result of comparison between vibration intensity of saidinternal combustion engine and said corrected determination value, andthereby determines whether knock has occurred or not using the sum ofeach of said integrated values of said corrected waveform.
 57. A knockdetermination method for an internal combustion engine, comprising thesteps of: detecting intensity of vibration of said internal combustionengine; detecting waveform of vibration of said internal combustionengine based on the detected intensity; calculating, for each of apredetermined plurality of crank angle ranges, an integrated valueintegrating the vibration intensity of said waveform; detecting anamount of change in said integrated value between ignition cycles foreach of said plurality of crank angle ranges; specifying a predeterminednumber of crank angle ranges in which the amount of change in saidintegrated value is larger, among said plurality of crank angle ranges;determining whether the integrated value in said specified ranges haschanged not because of knocking, if it is determined that the integratedvalue in said specified range has changed not because of knocking,correcting said detected vibration waveform such that amount of changein the integrated value in said specified range becomes smaller;calculating, for each of said plurality of crank angle ranges, anintegrated value integrating vibration intensities of said correctedwaveform; and determining whether knock has occurred or not using a sumof each of said integrated values of said corrected waveform.
 58. Theknock determination method for an internal combustion engine accordingto claim 57, wherein said step of correcting detected vibration waveformincludes the step of correcting, if it is determined that the integratedvalue in said specified range has changed not because of knocking, saiddetected vibration waveform such that the integrated value of saidspecified range becomes equal to an integrated value calculated in thelast ignition cycle, so that the amount of change of said integratedvalue becomes smaller.
 59. The knock determination method for aninternal combustion engine according to claim 58, wherein said step ofdetecting the amount of change in the integrated value includes the stepof detecting the amount of change of said integrated value based on adifference of said integrated values of continuous ignition cycles. 60.The knock determination method for an internal combustion engineaccording to claim 58, wherein said step of detecting the amount ofchange in the integrated value includes the step of detecting the amountof change of said integrated value based on an absolute value ofdifference of said integrated values of continuous ignition cycles. 61.The knock determination method for an internal combustion engineaccording to claim 57, further comprising the step of calculating anoperation value by smoothing said integrated value for each of saidplurality of crank angle ranges; wherein said step of correcting saiddetected vibration waveform includes the step of correcting, if it isdetermined that the integrated value in said specified range has changednot because of knocking, said detected vibration waveform such that theintegrated value of said specified range becomes equal to said operationvalue, so that the amount of change of said integrated value becomessmaller.
 62. The knock determination method for an internal combustionengine according to claim 61, wherein said step of detecting the amountof change in the integrated value includes the step of detecting theamount of change of said integrated value based on a difference betweensaid integrated value and said operation value.
 63. The knockdetermination method for an internal combustion engine according toclaim 61, wherein said step of detecting the amount of change in theintegrated value includes the step of detecting the amount of change ofsaid integrated value based on an absolute value of difference betweensaid integrated value and said operation value.
 64. The knockdetermination method for an internal combustion engine according toclaim 57, further comprising the step of specifying a crank angle havingan intensity higher than the intensity in a neighboring crank angle, ina search range determined with reference to said specified range;wherein said step of determining whether said integrated value haschanged not because of knocking includes the step of determining, whilea timing at which intensity becomes the highest in a waveform modeldefined as a reference of vibration in said internal combustion engineis matched with the specified crank angle, based on a result ofcomparison between the waveform and the waveform model in this state,whether the integrated value in said specified range has changed notbecause of knocking.
 65. The knock determination method for an internalcombustion engine according to claim 64, further comprising the step ofcalculating a coefficient corresponding to a difference between saidwaveform and said waveform model such that the coefficient becomeslarger as the difference between said waveform and said waveform modelbecomes smaller; wherein said step of determining whether saidintegrated value has changed not because of knocking includes the stepsof determining, if said coefficient is larger than a threshold value,that the integrated value in the specified range has changed because ofknocking, and determining, if said coefficient is smaller than thethreshold, that the integrated value in the specified range has changednot because of knocking.
 66. The knock determination method for aninternal combustion engine according to claim 57, wherein said step ofdetermining whether said integrated value has changed not because ofknocking includes the step of determining, if said specified crank angleis in a predetermined range, that the integrated value in said specifiedrange has changed not because of knocking.
 67. The knock determinationmethod for an internal combustion engine according to claim 57, whereinsaid step of specifying the range in which the amount of change in saidintegrated value is larger includes the step of specifying a pluralityof crank angle ranges in which the amount of change in said integratedvalue is larger, among said plurality of crank angle ranges; and saidstep of determining whether said integrated value has changed notbecause of knocking includes the step of determining whether theintegrated values in said plurality of specified ranges have changed notbecause of knocking.
 68. The knock determination method for an internalcombustion engine according to claim 67, further comprising the step ofinhibiting, if it is determined that the integrated value in at leastone of said plurality of specified ranges has changed because ofknocking, correction of said detected waveform.
 69. The knockdetermination method for an internal combustion engine according toclaim 67, wherein said step of correcting the detected vibrationwaveform includes the step of correcting, if it is determined that theintegrated value in at least one of said plurality of specified rangeshas changed not because of knocking, said detected vibration waveformsuch that the amount of change in the integrated value in the range inwhich said integrated value is determined to have changed not because ofknocking becomes smaller.
 70. The knock determination method for aninternal combustion engine according to claim 57, further comprising thestep of correcting a determination value used for determining whetherknock has occurred or not, using a sum of said integrated values of saidcorrected waveform; wherein said step of determining whether knock hasoccurred or not includes the step of determining whether knock hasoccurred or not based on a result of comparison between vibrationintensity of said internal combustion engine and said correcteddetermination value, and thereby determining whether knock has occurredor not using the sum of each of said integrated values of said correctedwaveform.
 71. A knock determination device for an internal combustionengine, comprising: means for detecting intensity of vibration of saidinternal combustion engine; means for detecting waveform of vibration ofsaid internal combustion engine based on the detected intensity; meansfor calculating, for each of a predetermined plurality of crank angleranges, an integrated value integrating the vibration intensity of saidwaveform; detecting means for detecting an amount of change in saidintegrated value between ignition cycles for each of said plurality ofcrank angle ranges; specifying means for specifying a predeterminednumber of crank angle ranges in which the amount of change in saidintegrated value is larger, among said plurality of crank angle ranges;first determining means for determining whether the integrated value insaid specified ranges has changed not because of knocking; correctingmeans for correcting, if it is determined that the integrated value insaid specified range has changed not because of knocking, said detectedvibration waveform such that amount of change in the integrated value insaid specified ranges becomes smaller; means for calculating for each ofsaid plurality of crank angle ranges, an integrated value integratingvibration intensities of said corrected waveform; and second determiningmeans for determining whether knock has occurred or not using a sum ofeach of said integrated values of said corrected waveform.
 72. The knockdetermination device for an internal combustion engine according toclaim 71, wherein said correcting means includes means for correcting,if it is determined that the integrated value in said specified rangeshas changed not because of knocking, said detected vibration waveformsuch that the integrated value of said specified range becomes equal toan integrated value calculated in the last ignition cycle, so that theamount of change of said integrated value becomes smaller.
 73. The knockdetermination device for an internal combustion engine according toclaim 72, wherein said detecting means includes means for detecting theamount of change of said integrated value based on a difference of saidintegrated values of continuous ignition cycles.
 74. The knockdetermination device for an internal combustion engine according toclaim 72, wherein said detecting means includes means for detecting theamount of change of said integrated value based on an absolute value ofdifference of said integrated values of continuous ignition cycles. 75.The knock determination device for an internal combustion engineaccording to claim 71, further comprising means for calculating anoperation value by smoothing said integrated value for each of saidplurality of crank angle ranges; wherein said correcting means includesmeans for correcting, if it is determined that the integrated value insaid specified range has changed not because of knocking, said detectedvibration waveform such that the integrated value of said specifiedrange becomes equal to said operation value, so that the amount ofchange of said integrated value becomes smaller.
 76. The knockdetermination device for an internal combustion engine according toclaim 75, wherein said detecting means includes means for detecting theamount of change of said integrated value based on a difference betweensaid integrated value and said operation value.
 77. The knockdetermination device for an internal combustion engine according toclaim 75, wherein said detecting means includes means for detecting theamount of change of said integrated value based on an absolute value ofdifference between said integrated value and said operation value. 78.The knock determination device for an internal combustion engineaccording to claim 71, further comprising means for specifying a crankangle having an intensity higher than the intensity of a neighboringcrank angle, in a search range determined with reference to saidspecified range; wherein said first determining means includes means fordetermining, while a timing at which intensity becomes the highest in awaveform model defined as a reference of vibration in said internalcombustion engine is matched with the specified crank angle, based on aresult of comparison between the waveform and the waveform model in thisstate, whether the integrated value in said specified range has changednot because of knocking.
 79. The knock determination device for aninternal combustion engine according to claim 78, further comprisingmeans for calculating a coefficient corresponding to a differencebetween said waveform and said waveform model such that the coefficientbecomes larger as the difference between said waveform and said waveformmodel becomes smaller; wherein said first determining means includesmeans for determining, if said coefficient is larger than a thresholdvalue, that the integrated value in the specified range has changedbecause of knocking, and means for determining, if said coefficient issmaller than the threshold, that the integrated value in the specifiedrange has changed not because of knocking.
 80. The knock determinationdevice for an internal combustion engine according to claim 71, whereinsaid first determining means includes means for determining, if saidspecified crank angle is in a predetermined range, that the integratedvalue in said specified range has changed not because of knocking. 81.The knock determination device for an internal combustion engineaccording to claim 71, wherein said specifying means includes means forspecifying a plurality of crank angle ranges in which the amount ofchange in said integrated value is larger, among said plurality of crankangle ranges; and said first determining means includes means fordetermining whether the integrated values in said plurality of specifiedranges have changed not because of knocking.
 82. The knock determinationdevice for an internal combustion engine according to claim 81, furthercomprising means for inhibiting, if it is determined that the integratedvalue in at least one of said plurality of specified ranges has changedbecause of knocking, correction of said detected waveform.
 83. The knockdetermination device for an internal combustion engine according toclaim 81, wherein said correcting means includes means for correcting,if it is determined that the integrated value in at least one of saidplurality of specified ranges has changed not because of knocking, saiddetected vibration waveform such that the amount of change in theintegrated value in the range in which said integrated value isdetermined to have changed not because of knocking becomes smaller. 84.The knock determination device for an internal combustion engineaccording to claim 71, further comprising means for correcting adetermination value used for determining whether knock has occurred ornot, using a sum of said integrated values of said corrected waveform;wherein said second determining means includes means for determiningwhether knock has occurred or not based on a result of comparisonbetween vibration intensity of said internal combustion engine and saidcorrected determination value, and thereby determining whether knock hasoccurred or not using the sum of each of said integrated values of saidcorrected waveform.